Merge pull request #36 from KGAudioLab/feat/2026-04-30-midi-device-recording

Feat/2026 04 30 midi device recording

README.md

@@ -23,6 +23,7 @@ K.G.Studio is a lightweight, modern DAW that runs entirely in the browser with *
 
 ## Latest Updates
 
+- **2026.05.02**: Added **audio track spectrogram visualization** — audio regions now display a real-time spectrogram overlay in the track grid. Added **Piano Roll hybrid mode**: open the piano roll on a MIDI region while an adjacent audio region's spectrogram is shown as a reference layer, letting you edit MIDI notes against the visual shape of the audio. Added **piano roll zoom in/out** with viewport-position preservation so the view stays anchored to the current playhead. Added **fine-tune region position**: nudge regions by small increments for precise placement. Also added cross-component playhead scroll synchronization so the main grid and piano roll stay in sync during playback.
 - **2026.04.29**: Added **Remix** and **Repaint** to the K.G.One Music Generator panel (powered by ACE-Step 1.5). **Remix** lets you cover an existing audio region in a new style — select an audio region, describe the target style and optionally provide new lyrics, and ACE-Step will re-perform the song with the prompted instrumentation and feel. **Repaint** lets you surgically re-generate a specific section of a song — set a loop range on the timeline to define the repaint window, then describe what you want that section to sound like; the rest of the song stays untouched. Both tools support the same import workflow as the other K.G.One tabs: preview the result in the built-in player, drag it onto a track, or click **Import Aligned to Source** to automatically place it below the original region in a new track.
 - **2026.04.24**: Added [**K.G.One Music Studio**](https://github.com/KGAudioLab/K.G.One) integration! When K.G.Studio connects to a local K.G.One server, the **K.G.One Music Generator** panel (magic wand button ✦ in the toolbar) becomes available with three AI-powered tools: **Full Song Generation** (powered by ACE-Step 1.5 — generate full-length songs from text prompts), **Clip Generation** (powered by Foundation-1 — generate instrument clips and MIDI loops from text), and **Stem Separation** (powered by python-audio-separator — split any audio into vocals, instrumentals, and more). Generated audio and MIDI can be previewed instantly and dragged directly onto your tracks. K.G.One runs entirely on your own machine (Windows/Linux, CUDA GPU required); see the [K.G.One repository](https://github.com/KGAudioLab/K.G.One) for setup instructions.
 - **2026.04.11**: Migrated project storage from IndexedDB to OPFS (Origin Private File System) with a folder-based structure for better media file handling. Added audio track support with WAV/MP3 import, playback, looping, and non-destructive region trimming. Added bounce-to-WAV/MP3 export via offline rendering.

package-lock.json

@@ -1,15 +1,16 @@
 {
   "name": "K.G.Studio",
-  "version": "0.10.0-build.20260411",
+  "version": "0.12.0-build.20260430",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "K.G.Studio",
-      "version": "0.10.0-build.20260411",
+      "version": "0.12.0-build.20260430",
       "dependencies": {
         "@breezystack/lamejs": "^1.2.7",
         "class-transformer": "^0.5.1",
+        "fft.js": "^4.0.4",
         "idb": "^8.0.3",
         "jszip": "^3.10.1",
         "openai": "^6.33.0",
@@ -4691,6 +4692,12 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/fft.js": {
+      "version": "4.0.4",
+      "resolved": "https://registry.npmjs.org/fft.js/-/fft.js-4.0.4.tgz",
+      "integrity": "sha512-f9c00hphOgeQTlDyavwTtu6RiK8AIFjD6+jvXkNkpeQ7rirK3uFWVpalkoS4LAwbdX7mfZ8aoBfFVQX1Re/8aw==",
+      "license": "MIT"
+    },
     "node_modules/figures": {
       "version": "5.0.0",
       "resolved": "https://registry.npmjs.org/figures/-/figures-5.0.0.tgz",

package.json

@@ -16,6 +16,7 @@
   "dependencies": {
     "@breezystack/lamejs": "^1.2.7",
     "class-transformer": "^0.5.1",
+    "fft.js": "^4.0.4",
     "idb": "^8.0.3",
     "jszip": "^3.10.1",
     "openai": "^6.33.0",

src/components/MainContent.css

@@ -10,7 +10,7 @@
 .main-content-wrapper {
   display: flex;
   flex-direction: column;
-  min-width: calc(200px + var(--max-number-of-bars) * var(--track-grid-bar-width)); /* info width + grid width */
+  min-width: calc(var(--track-info-panel-width) + var(--max-number-of-bars) * var(--track-grid-bar-width)); /* info width + grid width */
   min-height: fit-content;
   position: relative;
 }
@@ -19,7 +19,7 @@
   position: fixed;
   top: 50px;
   left: 0;
-  width: 200px;
+  width: var(--track-info-panel-width);
   height: 20px;
   background-color: #2d2d2d;
   border-bottom: 1px solid #3a3a3a;
@@ -42,7 +42,7 @@
   border-bottom: 1px solid #3a3a3a;
   background-color: #2d2d2d;
   z-index: 20;
-  margin-left: 200px; /* Offset for info-container */
+  margin-left: var(--track-info-panel-width); /* Offset for info-container */
   width: calc(var(--max-number-of-bars) * var(--track-grid-bar-width)); /* Exact width for 32 bars */
   cursor: pointer; /* Show pointer cursor on hover to indicate interactivity */
 }
@@ -80,7 +80,7 @@
 .info-container {
   position: sticky;
   left: 0;
-  width: 200px;
+  width: var(--track-info-panel-width);
   z-index: 1002;
   background-color: #2d2d2d;
   align-self: flex-start;

src/components/MainContent.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useEffect, useRef, useCallback } from 'react';
+import React, { useState, useEffect, useRef, useCallback, useLayoutEffect } from 'react';
 import './MainContent.css';
 import { createPortal } from 'react-dom';
 import { useProjectStore } from '../stores/projectStore';
@@ -10,7 +10,7 @@ import TrackInfoPanel from './track/TrackInfoPanel';
 import TrackGridPanel from './track/TrackGridPanel';
 import PianoRoll from './piano-roll/PianoRoll';
 import type { RegionUI } from './interfaces';
-import { DEBUG_MODE, BAR_NUMBERS_CONSTANTS } from '../constants';
+import { DEBUG_MODE, BAR_NUMBERS_CONSTANTS, TOOLBAR_CONSTANTS } from '../constants';
 import { useRegionOperations } from '../hooks/useRegionOperations';
 import { regionDeleteManager } from '../util/regionDeleteUtil';
 import { KGMainContentState } from '../core/state/KGMainContentState';
@@ -26,6 +26,7 @@ const MainContent: React.FC<MainContentProps> = ({
   const {
     tracks,
     maxBars,
+    barWidthMultiplier,
     reorderTracks,
     updateTrack,
     updateTrackProperties,
@@ -41,9 +42,17 @@ const MainContent: React.FC<MainContentProps> = ({
     activeRegionId,
     setShowPianoRoll,
     setActiveRegionId,
+    pianoRollMode,
+    openMidiPianoRoll,
+    openSpectrogramViewer,
+    openHybridMode,
+    hybridAudioRegionId,
     addTrack,
     addAudioTrack,
     projectName,
+    savedProjectName,
+    requestPianoRollScroll,
+    mainContentScrollRequest,
   } = useProjectStore();
 
   // State to store regions
@@ -88,6 +97,7 @@ const MainContent: React.FC<MainContentProps> = ({
   const mainContentRef = useRef<HTMLDivElement | null>(null);
   const expectedScrollLeftRef = useRef<number>(-1);
   const isPlayingRef = useRef(false);
+  const previousBarWidthMultiplierRef = useRef(barWidthMultiplier);
 
   // Refs for bar numbers and loop range drag functionality
   const barNumbersRef = useRef<HTMLDivElement | null>(null);
@@ -101,6 +111,37 @@ const MainContent: React.FC<MainContentProps> = ({
     isPlayingRef.current = isPlaying;
   }, [isPlaying]);
 
+  useLayoutEffect(() => {
+    const previousMultiplier = previousBarWidthMultiplierRef.current;
+    if (previousMultiplier === barWidthMultiplier) return;
+
+    previousBarWidthMultiplierRef.current = barWidthMultiplier;
+
+    const container = mainContentRef.current;
+    if (!container) return;
+
+    const infoWidth = parseInt(
+      getComputedStyle(document.documentElement).getPropertyValue('--track-info-panel-width')
+    ) || 200;
+    const visibleMusicWidth = Math.max(0, container.clientWidth - infoWidth);
+    const previousBarWidth = TOOLBAR_CONSTANTS.BASE_BAR_WIDTH * previousMultiplier;
+    const nextBarWidth = TOOLBAR_CONSTANTS.BASE_BAR_WIDTH * barWidthMultiplier;
+
+    if (visibleMusicWidth === 0 || previousBarWidth === 0 || nextBarWidth === 0) return;
+
+    const centerPixelBeforeZoom = container.scrollLeft + visibleMusicWidth / 2;
+    const anchorBeat = (centerPixelBeforeZoom / previousBarWidth) * timeSignature.numerator;
+    const targetPixel = (anchorBeat / timeSignature.numerator) * nextBarWidth;
+    const targetScrollLeft = targetPixel - visibleMusicWidth / 2;
+    const clampedScrollLeft = Math.max(
+      0,
+      Math.min(targetScrollLeft, container.scrollWidth - container.clientWidth)
+    );
+
+    expectedScrollLeftRef.current = clampedScrollLeft;
+    container.scrollLeft = clampedScrollLeft;
+  }, [barWidthMultiplier, timeSignature]);
+
   // Detect manual horizontal scroll during playback
   useEffect(() => {
     const container = mainContentRef.current;
@@ -130,8 +171,10 @@ const MainContent: React.FC<MainContentProps> = ({
     ) || 40;
     const playheadPixel = barPosition * barWidth;
 
-    // Center the playhead in the visible grid area (excluding the 200px sticky info panel)
+    // Center the playhead in the visible grid area (excluding the sticky info panel)
-    const infoWidth = 200;
+    const infoWidth = parseInt(
+      getComputedStyle(document.documentElement).getPropertyValue('--track-info-panel-width')
+    ) || 200;
     const targetScrollLeft = playheadPixel - (container.clientWidth - infoWidth) / 2;
     const clampedScrollLeft = Math.max(
       0,
@@ -142,6 +185,36 @@ const MainContent: React.FC<MainContentProps> = ({
     container.scrollLeft = clampedScrollLeft;
   }, [playheadPosition, isPlaying, autoScrollEnabled, timeSignature]);
 
+  // Handle scroll requests from piano roll header clicks
+  useEffect(() => {
+    if (mainContentScrollRequest === null) return;
+
+    const container = mainContentRef.current;
+    if (!container) return;
+
+    const beatsPerBar = timeSignature.numerator;
+    const barPosition = mainContentScrollRequest / beatsPerBar;
+    const barWidth = parseInt(
+      getComputedStyle(document.documentElement).getPropertyValue('--track-grid-bar-width')
+    ) || 40;
+    const playheadPixel = barPosition * barWidth;
+
+    // Center the playhead in the visible grid area (excluding the sticky info panel)
+    const infoWidth = parseInt(
+      getComputedStyle(document.documentElement).getPropertyValue('--track-info-panel-width')
+    ) || 200;
+    const targetScrollLeft = playheadPixel - (container.clientWidth - infoWidth) / 2;
+    const clampedScrollLeft = Math.max(
+      0,
+      Math.min(targetScrollLeft, container.scrollWidth - container.clientWidth)
+    );
+
+    container.scrollLeft = clampedScrollLeft;
+
+    // Clear the request after handling
+    useProjectStore.setState({ mainContentScrollRequest: null });
+  }, [mainContentScrollRequest, timeSignature]);
+
   // Effect to verify track updates
   useEffect(() => {
     // Check for pending updates
@@ -433,8 +506,9 @@ const MainContent: React.FC<MainContentProps> = ({
       }
     }
 
-    // If piano roll is visible, set this region as the active region
+    // Keep the active piano roll region in sync when that same region is updated.
-    if (showPianoRoll) {
+    // Do not switch the editor to an unrelated region from generic move/resize updates.
+    if (showPianoRoll && activeRegionId === regionId) {
       setActiveRegionId(regionId);
 
       if (DEBUG_MODE.MAIN_CONTENT) {
@@ -508,6 +582,16 @@ const MainContent: React.FC<MainContentProps> = ({
     const track = tracks.find(t => t.getId().toString() === region.trackId);
     if (!track) return;
     setSelectedTrack(track.getId().toString());
+
+    // If the piano roll window is already open, follow the selected region's type
+    if (showPianoRoll) {
+      const coreRegion = track.getRegions().find(r => r.getId() === regionId);
+      if (coreRegion?.getCurrentType() === 'KGAudioRegion') {
+        openSpectrogramViewer(regionId);
+      } else if (coreRegion?.getCurrentType() === 'KGMidiRegion') {
+        openMidiPianoRoll(regionId);
+      }
+    }
   };
 
   // Handle explicit pencil action: select region and open piano roll
@@ -528,11 +612,29 @@ const MainContent: React.FC<MainContentProps> = ({
     // Reuse selection logic
     handleRegionClick(regionId);
 
-    // Activate and show piano roll
+    // Activate and show piano roll in midi-edit mode
-    setActiveRegionId(regionId);
+    openMidiPianoRoll(regionId);
-    setShowPianoRoll(true);
   };
 
+  // Handle spectrogram viewer open
+  const handleOpenSpectrogram = (regionId: string) => {
+    handleRegionClick(regionId);
+    openSpectrogramViewer(regionId);
+  };
+
+  // Handle hybrid mode open (+ button clicked on opposite-type region)
+  const handleOpenHybrid = (regionId: string) => {
+    if (pianoRollMode === 'midi-edit' && activeRegionId) {
+      openHybridMode(activeRegionId, regionId);
+    } else if (pianoRollMode === 'spectrogram' && activeRegionId) {
+      openHybridMode(regionId, activeRegionId);
+    }
+  };
+
+  // + button is visible only when piano roll is open and mode is not hybrid
+  const showHybridButtonForAudio = showPianoRoll && pianoRollMode === 'midi-edit';
+  const showHybridButtonForMidi  = showPianoRoll && pianoRollMode === 'spectrogram';
+
   // Handle piano roll close
   const handlePianoRollClose = () => {
     setShowPianoRoll(false);
@@ -739,6 +841,7 @@ const MainContent: React.FC<MainContentProps> = ({
             const clickPosition = calculatePlayheadFromMouse(e.clientX);
             if (clickPosition !== null) {
               setPlayheadPosition(clickPosition);
+              requestPianoRollScroll(clickPosition);
 
               if (DEBUG_MODE.MAIN_CONTENT) {
                 console.log(`Single click on bar numbers - Set playhead to: ${clickPosition}`);
@@ -764,7 +867,7 @@ const MainContent: React.FC<MainContentProps> = ({
       document.removeEventListener('mousemove', handleMouseMove);
       document.removeEventListener('mouseup', handleMouseUp);
     };
-  }, [calculateBarIndexFromMouse, calculatePlayheadFromMouse, setPlayheadPosition]);
+  }, [calculateBarIndexFromMouse, calculatePlayheadFromMouse, setPlayheadPosition, requestPianoRollScroll]);
 
   const { showInstrumentSelection, isLooping, loopingRange } = useProjectStore();
 
@@ -824,16 +927,49 @@ const MainContent: React.FC<MainContentProps> = ({
             onRegionUpdated={handleRegionUpdated}
             onRegionClick={handleRegionClick}
             onOpenPianoRoll={handleOpenPianoRoll}
+            onOpenSpectrogram={handleOpenSpectrogram}
+            showHybridButtonForAudio={showHybridButtonForAudio}
+            showHybridButtonForMidi={showHybridButtonForMidi}
+            onOpenHybrid={handleOpenHybrid}
             onExternalDropComplete={handleExternalDropComplete}
           />
         </div>
       </div>
 
-      {/* Piano Roll - render using portal */}
+      {/* Piano Roll / Spectrogram Viewer - render using portal */}
       {showPianoRoll && createPortal(
         <PianoRoll
           onClose={handlePianoRollClose}
           regionId={activeRegionId}
+          mode={pianoRollMode}
+          audioRegion={(() => {
+            // spectrogram mode: audio region IS the activeRegionId
+            // hybrid mode: audio region is hybridAudioRegionId
+            const audioId = pianoRollMode === 'spectrogram' ? activeRegionId
+                          : pianoRollMode === 'hybrid'      ? hybridAudioRegionId
+                          : null;
+            if (!audioId) return undefined;
+            for (const track of tracks) {
+              const region = track.getRegions().find(r => r.getId() === audioId);
+              if (region && region.getCurrentType() === 'KGAudioRegion') {
+                return region as unknown as KGAudioRegion;
+              }
+            }
+            return undefined;
+          })()}
+          trackId={(() => {
+            const audioId = pianoRollMode === 'spectrogram' ? activeRegionId
+                          : pianoRollMode === 'hybrid'      ? hybridAudioRegionId
+                          : null;
+            if (!audioId) return undefined;
+            for (const track of tracks) {
+              if (track.getRegions().some(r => r.getId() === audioId)) {
+                return track.getId().toString();
+              }
+            }
+            return undefined;
+          })()}
+          projectName={savedProjectName}
         />,
         document.body
       )}

src/components/piano-roll/PianoGrid.tsx

@@ -6,6 +6,8 @@ import { isModifierKeyPressed } from '../../util/osUtil';
 import { generatePianoGridBackground, getMatchingChordsForPitch } from '../../util/scaleUtil';
 import type { KeySignature } from '../../core/KGProject';
 import { KGPianoRollState } from '../../core/state/KGPianoRollState';
+import SpectrogramCanvas from './SpectrogramCanvas';
+import type { KGAudioRegion } from '../../core/region/KGAudioRegion';
 
 interface PianoGridProps {
   gridRef: MutableRefObject<HTMLDivElement | null>;
@@ -24,6 +26,15 @@ interface PianoGridProps {
   selectedMode: string;
   keySignature: KeySignature;
   chordGuide: string;
+  audioRegion?: KGAudioRegion;
+  trackId?: string;
+  projectName?: string;
+  bpm?: number;
+  spectrogramThresholdDb?: number;
+  spectrogramPower?: number;
+  pianoRollZoom?: number;
+  mode?: 'midi-edit' | 'spectrogram' | 'hybrid';
+  onSpectrogramLoadingChange?: (loading: boolean) => void;
 }
 
 interface CursorPosition {
@@ -44,7 +55,15 @@ const PianoGrid: React.FC<PianoGridProps> = ({
   regionStartBeat = 0,
   selectedMode,
   keySignature,
-  chordGuide
+  chordGuide,
+  audioRegion,
+  trackId,
+  projectName,
+  bpm = 120,
+  spectrogramThresholdDb = -25,
+  spectrogramPower = 0.5,
+  pianoRollZoom = 1,
+  onSpectrogramLoadingChange,
 }) => {
   const [cursorPosition, setCursorPosition] = useState<CursorPosition | null>(null);
   const [isModifierPressed, setIsModifierPressed] = useState(false);
@@ -209,13 +228,27 @@ const PianoGrid: React.FC<PianoGridProps> = ({
       <div
         className={`piano-grid ${isModifierPressed ? 'pencil-cursor' : ''}`}
         ref={gridRef}
-        style={{ backgroundImage }}
+        style={{ backgroundImage: audioRegion ? undefined : backgroundImage }}
         onDoubleClick={onDoubleClick}
         onClick={onClick}
         onMouseDown={(e) => onMouseDown(e)}
         onMouseMove={handleMouseMove}
         onMouseLeave={handleMouseLeave}
       >
+        {/* Spectrogram layer — rendered at z-index 0, behind all highlights and notes */}
+        {audioRegion && trackId && projectName && (
+          <SpectrogramCanvas
+            audioRegion={audioRegion}
+            trackId={trackId}
+            projectName={projectName}
+            bpm={bpm}
+            thresholdDb={spectrogramThresholdDb}
+            power={spectrogramPower}
+            zoom={pianoRollZoom}
+            onLoadingChange={onSpectrogramLoadingChange}
+          />
+        )}
+
         {/* Cursor Highlights */}
         {cursorPosition && (
           <>

src/components/piano-roll/PianoGridHeader.tsx

@@ -14,7 +14,7 @@ const PianoGridHeader: React.FC<PianoGridHeaderProps> = ({
   timeSignature = { numerator: 4, denominator: 4 } // Default to 4/4 if not provided
 }) => {
   // Get store access for playhead position updates
-  const { setPlayheadPosition } = useProjectStore();
+  const { setPlayheadPosition, requestMainContentScroll } = useProjectStore();
   
   // Refs for drag functionality
   const isDraggingRef = useRef(false);
@@ -124,6 +124,7 @@ const PianoGridHeader: React.FC<PianoGridHeaderProps> = ({
       }
 
       setPlayheadPosition(newPosition);
+      requestMainContentScroll(newPosition);
     }
   };
 

src/components/piano-roll/PianoRoll.css

@@ -77,10 +77,17 @@
   /* Ensure toolbar and its dropdowns appear above piano roll content */
 }
 
+.piano-roll-toolbar .tool-button {
+  width: 20px;
+  height: 20px;
+}
+
 /* Override pointer-events for piano roll toolbar sections */
 .piano-roll-toolbar .toolbar-left,
 .piano-roll-toolbar .toolbar-right {
   pointer-events: auto;
+  /* max-width: 70%; */
+  width: auto;
 }
 
 .piano-roll-toolbar .quant-button {
@@ -96,12 +103,44 @@
   left: 0;
 }
 
+/* Spectrogram toolbar controls */
+.spectrogram-toolbar-controls {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  margin-left: 5px;
+}
+
+.spectrogram-control-label {
+  font-size: 10px;
+  color: #aaa;
+  white-space: nowrap;
+}
+
+.spectrogram-threshold-slider {
+  /* Match the visual width of the Qua. Pos. / Qua. Len. buttons (~80px) */
+  width: 80px;
+  height: 4px;
+  accent-color: #7a9ccf;
+  cursor: pointer;
+  margin: 0;
+}
+
+.spectrogram-threshold-value {
+  font-size: 10px;
+  color: #e0e0e0;
+  min-width: 30px;
+  text-align: right;
+  white-space: nowrap;
+}
+
 .piano-roll-title {
   flex: 1;
   text-align: center;
-  font-size: 14px;
+  font-size: 12px;
+  font-weight: bold;
   color: #e0e0e0;
-  text-transform: uppercase;
+  /* text-transform: uppercase; */
   cursor: pointer;
   padding: 5px;
   border-radius: 3px;
@@ -120,13 +159,37 @@
   color: #ff4444;
 }
 
+.piano-roll-content-outer {
+  position: relative;
+  flex: 1;
+  overflow: hidden;
+}
+
 .piano-roll-content {
   display: flex;
   flex-direction: column;
-  flex: 1;
+  height: 100%;
   overflow: auto;
 }
 
+.spectrogram-loading-overlay {
+  position: absolute;
+  inset: 0;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  pointer-events: none;
+  z-index: 100;
+}
+
+.spectrogram-loading-label {
+  padding: 6px 10px;
+  background: rgba(0, 0, 0, 0.6);
+  color: #aaa;
+  font-size: 11px;
+  border-radius: 3px;
+}
+
 .piano-grid-header {
   display: grid;
   grid-template-columns: repeat(var(--max-number-of-bars), var(--region-grid-bar-width));
@@ -276,3 +339,31 @@
   justify-content: center;
   z-index: 100;
 }
+
+.piano-roll-zoom-popup {
+  position: absolute;
+  top: 100%;
+  right: 0;
+  background-color: #2d2d2d;
+  border: 1px solid #444;
+  border-radius: 3px;
+  padding: 8px 12px;
+  z-index: 1500;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
+  white-space: nowrap;
+  margin-top: 2px;
+}
+
+.piano-roll-zoom-popup input[type="range"] {
+  width: 120px;
+}
+
+.piano-roll-zoom-value {
+  font-size: 12px;
+  color: #e0e0e0;
+  min-width: 20px;
+  text-align: center;
+}

src/components/piano-roll/PianoRoll.tsx

@@ -1,10 +1,11 @@
-import React, { useRef, useEffect, useState, useCallback } from 'react';
+import React, { useRef, useEffect, useState, useCallback, useLayoutEffect } from 'react';
 import './PianoRoll.css';
 import type { MouseEvent } from 'react';
 import { useProjectStore } from '../../stores/projectStore';
 import { FaGripLines } from 'react-icons/fa';
 import { KGMidiRegion } from '../../core/region/KGMidiRegion';
-import { DEBUG_MODE, PIANO_ROLL_CONSTANTS } from '../../constants';
+import type { KGAudioRegion } from '../../core/region/KGAudioRegion';
+import { DEBUG_MODE, PIANO_ROLL_CONSTANTS, TOOLBAR_CONSTANTS } from '../../constants';
 import PianoRollHeader from './PianoRollHeader';
 import PianoRollToolbar from './PianoRollToolbar';
 import PianoRollContent from './PianoRollContent';
@@ -22,19 +23,36 @@ interface PianoRollProps {
   regionId: string | null;
   initialPosition?: { x: number; y: number };
   initialSize?: { width: number; height: number };
+  mode?: 'midi-edit' | 'spectrogram' | 'hybrid';
+  audioRegion?: KGAudioRegion;
+  trackId?: string;
+  projectName?: string;
 }
 
 const PianoRoll: React.FC<PianoRollProps> = ({
   onClose,
   regionId,
   initialPosition,
-  initialSize
+  initialSize,
+  mode = 'midi-edit',
+  audioRegion,
+  trackId,
+  projectName,
 }) => {
-  const { maxBars, tracks, updateTrack, timeSignature, showChatBox, showInstrumentSelection, keySignature, selectedMode, setSelectedMode, playheadPosition, isPlaying, autoScrollEnabled } = useProjectStore();
+  const isSpectrogram = mode === 'spectrogram';
+  const isHybrid = mode === 'hybrid';
+  const { maxBars, tracks, updateTrack, timeSignature, showChatBox, showInstrumentSelection, keySignature, selectedMode, setSelectedMode, playheadPosition, isPlaying, autoScrollEnabled, bpm, pianoRollScrollRequest } = useProjectStore();
   
   // Tool state for piano roll
   const [activeTool, setActiveTool] = useState<'pointer' | 'pencil'>('pointer');
 
+  // Spectrogram controls (only used in spectrogram mode)
+  const [spectrogramThresholdDb, setSpectrogramThresholdDb] = useState<number>(-25);
+  const [spectrogramPower, setSpectrogramPower] = useState<number>(0.5);
+
+  // Piano roll zoom (1x–8x); updates --region-grid-beat-width CSS variable
+  const [pianoRollZoom, setPianoRollZoom] = useState<number>(1);
+  
   // Quantization state
   const [quantPosition, setQuantPosition] = useState<string>('1/8');
   const [quantLength, setQuantLength] = useState<string>('1/8');
@@ -63,6 +81,7 @@ const PianoRoll: React.FC<PianoRollProps> = ({
   // Refs for auto-scroll during playback
   const pianoRollExpectedScrollLeftRef = useRef<number>(-1);
   const pianoRollIsPlayingRef = useRef(false);
+  const pendingZoomAnchorBeatRef = useRef<number | null>(null);
 
   // Ref for storing the setNoteUpdateCounter function
   const triggerNoteUpdateRef = useRef<React.Dispatch<React.SetStateAction<number>> | null>(null);
@@ -140,22 +159,22 @@ const PianoRoll: React.FC<PianoRollProps> = ({
       return;
     }
 
-    // Find the region in the tracks
+    let found: KGMidiRegion | null = null;
     for (const track of tracks) {
-      const regions = track.getRegions();
+      const region = track.getRegions().find(r => r.getId() === regionId);
-      const region = regions.find(r => r.getId() === regionId);
-      
       if (region && region instanceof KGMidiRegion) {
-        setActiveRegion(region);
+        found = region;
-        
-        if (DEBUG_MODE.PIANO_ROLL) {
-          console.log(`Active region set in PianoRoll: ${region.getId()}`);
-          console.log(`Region details: name=${region.getName()}, trackId=${region.getTrackId()}, trackIndex=${region.getTrackIndex()}`);
-        }
-        
         break;
       }
     }
+
+    // Always update — clears stale MIDI region when switching to an audio region
+    setActiveRegion(found);
+
+    if (found && DEBUG_MODE.PIANO_ROLL) {
+      console.log(`Active region set in PianoRoll: ${found.getId()}`);
+      console.log(`Region details: name=${found.getName()}, trackId=${found.getTrackId()}, trackIndex=${found.getTrackIndex()}`);
+    }
   }, [regionId, tracks]);
 
   // Sync local state with KGPianoRollState on mount
@@ -595,6 +614,30 @@ const PianoRoll: React.FC<PianoRollProps> = ({
     }
   }, [quantizeSelectedNotes, quantizeNoteLength]);
 
+  const handleZoomChange = useCallback((nextZoom: number) => {
+    if (nextZoom === pianoRollZoom) return;
+
+    const container = pianoRollContentRef.current;
+    pendingZoomAnchorBeatRef.current = null;
+    if (container) {
+      const keysWidth = parseInt(
+        getComputedStyle(document.documentElement).getPropertyValue('--region-piano-key-width')
+      ) || 60;
+      const visibleMusicWidth = Math.max(0, container.clientWidth - keysWidth);
+      const beatWidth = parseInt(
+        getComputedStyle(document.documentElement).getPropertyValue('--region-grid-beat-width')
+      ) || TOOLBAR_CONSTANTS.BASE_BAR_WIDTH;
+
+      if (visibleMusicWidth > 0 && beatWidth > 0) {
+        pendingZoomAnchorBeatRef.current = (container.scrollLeft + visibleMusicWidth / 2) / beatWidth;
+      } else {
+        pendingZoomAnchorBeatRef.current = null;
+      }
+    }
+
+    setPianoRollZoom(nextZoom);
+  }, [pianoRollZoom]);
+
   // Calculate C4 position and scroll to it when piano roll opens
   useEffect(() => {
     if (pianoRollContentRef.current) {
@@ -671,6 +714,66 @@ const PianoRoll: React.FC<PianoRollProps> = ({
     container.scrollLeft = clampedScrollLeft;
   }, [playheadPosition, isPlaying, autoScrollEnabled]);
 
+  // Handle scroll requests from main content bar numbers clicks
+  useEffect(() => {
+    if (pianoRollScrollRequest === null) return;
+
+    const container = pianoRollContentRef.current;
+    if (!container) return;
+
+    const beatWidth = parseInt(
+      getComputedStyle(document.documentElement).getPropertyValue('--region-grid-beat-width')
+    ) || 40;
+    const playheadPixel = pianoRollScrollRequest * beatWidth;
+
+    // Center the playhead in the visible grid area (excluding the 60px sticky piano keys panel)
+    const keysWidth = parseInt(
+      getComputedStyle(document.documentElement).getPropertyValue('--region-piano-key-width')
+    ) || 60;
+    const targetScrollLeft = playheadPixel - (container.clientWidth - keysWidth) / 2;
+    const clampedScrollLeft = Math.max(
+      0,
+      Math.min(targetScrollLeft, container.scrollWidth - container.clientWidth)
+    );
+
+    container.scrollLeft = clampedScrollLeft;
+
+    // Clear the request after handling
+    useProjectStore.setState({ pianoRollScrollRequest: null });
+  }, [pianoRollScrollRequest]);
+
+  // Update --region-grid-beat-width when zoom changes and preserve the centered beat position.
+  useLayoutEffect(() => {
+    const beatWidth = TOOLBAR_CONSTANTS.BASE_BAR_WIDTH * pianoRollZoom;
+    document.documentElement.style.setProperty('--region-grid-beat-width', `${beatWidth}px`);
+    if (triggerNoteUpdateRef.current) {
+      triggerNoteUpdateRef.current(prev => prev + 1);
+    }
+
+    const anchorBeat = pendingZoomAnchorBeatRef.current;
+    const container = pianoRollContentRef.current;
+    if (anchorBeat !== null && container) {
+      const keysWidth = parseInt(
+        getComputedStyle(document.documentElement).getPropertyValue('--region-piano-key-width')
+      ) || 60;
+      const visibleMusicWidth = Math.max(0, container.clientWidth - keysWidth);
+      const targetPixel = anchorBeat * beatWidth;
+      const targetScrollLeft = targetPixel - visibleMusicWidth / 2;
+      const clampedScrollLeft = Math.max(
+        0,
+        Math.min(targetScrollLeft, container.scrollWidth - container.clientWidth)
+      );
+
+      pianoRollExpectedScrollLeftRef.current = clampedScrollLeft;
+      container.scrollLeft = clampedScrollLeft;
+      pendingZoomAnchorBeatRef.current = null;
+    }
+
+    return () => {
+      document.documentElement.style.setProperty('--region-grid-beat-width', '40px');
+    };
+  }, [pianoRollZoom]);
+
   // Scroll horizontally to the active region's starting bar
   useEffect(() => {
     if (pianoRollContentRef.current && activeRegion) {
@@ -855,6 +958,12 @@ const PianoRoll: React.FC<PianoRollProps> = ({
 
   // Get the title for the piano roll based on the active region
   const getPianoRollTitle = () => {
+    if (isSpectrogram) return audioRegion ? `SPECTROGRAM — ${audioRegion.getName()}` : 'SPECTROGRAM';
+    if (isHybrid) {
+      const midiName = activeRegion?.getName() ?? 'MIDI';
+      const audioName = audioRegion?.getName() ?? 'Audio';
+      return `${midiName} + ${audioName}`;
+    }
     if (!activeRegion) return "EDIT NOTE CLIP";
     
     // Calculate the bar and beat position of the region
@@ -901,6 +1010,13 @@ const PianoRoll: React.FC<PianoRollProps> = ({
         chordGuide={chordGuide}
         onChordGuideChange={handleChordGuideSelect}
         blinkButton={blinkButton}
+        mode={mode}
+        thresholdDb={spectrogramThresholdDb}
+        onThresholdChange={setSpectrogramThresholdDb}
+        power={spectrogramPower}
+        onPowerChange={setSpectrogramPower}
+        zoom={pianoRollZoom}
+        onZoomChange={handleZoomChange}
       />
 
       <PianoRollContent
@@ -916,6 +1032,14 @@ const PianoRoll: React.FC<PianoRollProps> = ({
         selectedMode={selectedMode}
         keySignature={keySignature}
         chordGuide={chordGuide}
+        mode={mode}
+        audioRegion={audioRegion}
+        trackId={trackId}
+        projectName={projectName}
+        bpm={bpm}
+        spectrogramThresholdDb={spectrogramThresholdDb}
+        spectrogramPower={spectrogramPower}
+        pianoRollZoom={pianoRollZoom}
       />
       
       <div 

src/components/piano-roll/PianoRollContent.tsx

@@ -1,4 +1,4 @@
-import React, { useMemo, useState, useRef, useEffect } from 'react';
+import React, { useMemo, useState, useRef, useEffect, useCallback } from 'react';
 import { DEBUG_MODE } from '../../constants';
 import { KGMidiRegion } from '../../core/region/KGMidiRegion';
 import { KGMidiNote } from '../../core/midi/KGMidiNote';
@@ -12,6 +12,7 @@ import PianoGrid from './PianoGrid';
 import { useNoteOperations } from '../../hooks/useNoteOperations';
 import { useNoteSelection } from '../../hooks/useNoteSelection';
 import type { KeySignature } from '../../core/KGProject';
+import type { KGAudioRegion } from '../../core/region/KGAudioRegion';
 
 interface PianoRollContentProps {
   contentRef: React.MutableRefObject<HTMLDivElement | null>;
@@ -26,6 +27,14 @@ interface PianoRollContentProps {
   selectedMode: string;
   keySignature: KeySignature;
   chordGuide: string;
+  mode?: 'midi-edit' | 'spectrogram' | 'hybrid';
+  audioRegion?: KGAudioRegion;
+  trackId?: string;
+  projectName?: string;
+  bpm?: number;
+  spectrogramThresholdDb?: number;
+  spectrogramPower?: number;
+  pianoRollZoom?: number;
 }
 
 const PianoRollContent: React.FC<PianoRollContentProps> = ({
@@ -40,8 +49,22 @@ const PianoRollContent: React.FC<PianoRollContentProps> = ({
   onSetDeleteNotesTrigger,
   selectedMode,
   keySignature,
-  chordGuide
+  chordGuide,
+  mode = 'midi-edit',
+  audioRegion,
+  trackId,
+  projectName,
+  bpm = 120,
+  spectrogramThresholdDb = -25,
+  spectrogramPower = 0.5,
+  pianoRollZoom = 1,
 }) => {
+  const isSpectrogram = mode === 'spectrogram';
+  const [spectrogramLoading, setSpectrogramLoading] = useState(false);
+  const handleSpectrogramLoadingChange = useCallback((loading: boolean) => {
+    setSpectrogramLoading(loading);
+  }, []);
+
   // Get KGCore instance
   const core = KGCore.instance();
 
@@ -105,9 +128,8 @@ const PianoRollContent: React.FC<PianoRollContentProps> = ({
 
   // Combined click handler for both pointer and pencil modes
   const handleCombinedClick = (e: React.MouseEvent) => {
-    // Handle selection click (pointer mode)
+    if (isSpectrogram) return;
     handleBackgroundClick(e);
-    // Handle pencil mode note creation
     handleGridClick(e);
   };
 
@@ -144,7 +166,7 @@ const PianoRollContent: React.FC<PianoRollContentProps> = ({
 
   // Memoize the notes rendering to prevent unnecessary recalculations
   const memoizedNotes = useMemo(() => {
-    if (!activeRegion) return null;
+    if (isSpectrogram || !activeRegion) return null;
     
     if (DEBUG_MODE.PIANO_ROLL) {
       console.log(`Rendering notes for region: ${activeRegion.getId()}`);
@@ -219,7 +241,7 @@ const PianoRollContent: React.FC<PianoRollContentProps> = ({
         />
       );
     });
-  }, [activeRegion, noteUpdateCounter, resizingNoteId, draggingNoteId, tempNoteStyles, selectedNoteIds, selectionBoxRender, tracks]);
+  }, [mode, activeRegion, noteUpdateCounter, resizingNoteId, draggingNoteId, tempNoteStyles, selectedNoteIds, selectionBoxRender, tracks]);
 
   const recordingNoteOverlays = useMemo(() => {
     if (!isRecording || !activeRegion || recordingNotes.length === 0) return null;
@@ -240,31 +262,48 @@ const PianoRollContent: React.FC<PianoRollContentProps> = ({
   }, [isRecording, recordingNotes, activeRegion]);
 
   return (
-    <div
+    <div className="piano-roll-content-outer">
-      className="piano-roll-content"
+      <div
-      ref={contentRef}
+        className="piano-roll-content"
-    >
+        ref={contentRef}
-      <PianoGridHeader maxBars={maxBars} timeSignature={timeSignature} />
+      >
+        <PianoGridHeader maxBars={maxBars} timeSignature={timeSignature} />
 
-      <div className="piano-roll-body">
+        <div className="piano-roll-body">
-        <PianoKeys activeRegion={activeRegion} />
+          <PianoKeys activeRegion={activeRegion} />
 
-        <PianoGrid
+          <PianoGrid
-          gridRef={pianoGridRef}
+            gridRef={pianoGridRef}
-          onDoubleClick={handleGridDoubleClick}
+            onDoubleClick={isSpectrogram ? () => {} : handleGridDoubleClick}
-          onClick={handleCombinedClick}
+            onClick={isSpectrogram ? () => {} : handleCombinedClick}
-          onMouseDown={handleBackgroundMouseDown}
+            onMouseDown={isSpectrogram ? () => {} : handleBackgroundMouseDown}
-          isBoxSelecting={isBoxSelectingRef.current}
+            isBoxSelecting={isSpectrogram ? false : isBoxSelectingRef.current}
-          selectionBox={selectionBoxRef.current}
+            selectionBox={isSpectrogram ? { startX: 0, startY: 0, endX: 0, endY: 0 } : selectionBoxRef.current}
-          regionStartBeat={activeRegion?.getStartFromBeat() || 0}
+            regionStartBeat={activeRegion?.getStartFromBeat() || 0}
-          selectedMode={selectedMode}
+            selectedMode={selectedMode}
-          keySignature={keySignature}
+            keySignature={keySignature}
-          chordGuide={chordGuide}
+            chordGuide={chordGuide}
-        >
+            audioRegion={audioRegion}
-          {memoizedNotes}
+            trackId={trackId}
-          {recordingNoteOverlays}
+            projectName={projectName}
-        </PianoGrid>
+            bpm={bpm}
+            spectrogramThresholdDb={spectrogramThresholdDb}
+            spectrogramPower={spectrogramPower}
+            pianoRollZoom={pianoRollZoom}
+            onSpectrogramLoadingChange={handleSpectrogramLoadingChange}
+          >
+            {memoizedNotes}
+            {!isSpectrogram && recordingNoteOverlays}
+          </PianoGrid>
+        </div>
       </div>
+      {spectrogramLoading && (
+        <div className="spectrogram-loading-overlay">
+          <div className="spectrogram-loading-label">
+            Computing spectrogram…
+          </div>
+        </div>
+      )}
     </div>
   );
 };

src/components/piano-roll/PianoRollHeader.tsx

@@ -19,12 +19,6 @@ const PianoRollHeader: React.FC<PianoRollHeaderProps> = ({
       className="piano-roll-header"
       onMouseDown={onMouseDown}
     >
-      <button 
-        className="close-button"
-        onClick={onClose}
-      >
-        <FaTimes />
-      </button>
       <div 
         className="piano-roll-title"
         onClick={onTitleClick}
@@ -32,6 +26,12 @@ const PianoRollHeader: React.FC<PianoRollHeaderProps> = ({
       >
         {title}
       </div>
+      <button 
+        className="close-button"
+        onClick={onClose}
+      >
+        <FaTimes />
+      </button>
     </div>
   );
 };

src/components/piano-roll/PianoRollToolbar.tsx

@@ -4,6 +4,13 @@ import { KGDropdown } from '../common';
 import { KGPianoRollState } from '../../core/state/KGPianoRollState';
 import { KGCore } from '../../core/KGCore';
 
+const POWER_OPTIONS = [
+  { label: 'Linear', value: '1.0' },
+  { label: '√ (default)', value: '0.5' },
+  { label: 'Mild', value: '0.4' },
+  { label: 'Strong', value: '0.3' },
+];
+
 interface PianoRollToolbarProps {
   activeTool: 'pointer' | 'pencil';
   onToolSelect: (tool: 'pointer' | 'pencil') => void;
@@ -17,6 +24,13 @@ interface PianoRollToolbarProps {
   chordGuide: string;
   onChordGuideChange: (value: string) => void;
   blinkButton?: string | null;
+  mode?: 'midi-edit' | 'spectrogram' | 'hybrid';
+  thresholdDb?: number;
+  onThresholdChange?: (db: number) => void;
+  power?: number;
+  onPowerChange?: (power: number) => void;
+  zoom: number;
+  onZoomChange: (value: number) => void;
 }
 
 const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
@@ -31,79 +45,150 @@ const PianoRollToolbar: React.FC<PianoRollToolbarProps> = ({
   onModeChange,
   chordGuide,
   onChordGuideChange,
-  blinkButton = null
+  blinkButton = null,
+  mode = 'midi-edit',
+  thresholdDb = -25,
+  onThresholdChange,
+  power = 0.5,
+  onPowerChange,
+  zoom,
+  onZoomChange,
 }) => {
+  const isSpectrogram = mode === 'spectrogram';
+  const showMidiControls = mode !== 'spectrogram';   // midi-edit and hybrid
+  const showSpecControls = mode === 'spectrogram' || mode === 'hybrid';
+
+  const [showZoomSlider, setShowZoomSlider] = React.useState(false);
+  const zoomSliderRef = React.useRef<HTMLDivElement>(null);
+
+  React.useEffect(() => {
+    if (!showZoomSlider) return;
+    const handleClickOutside = (e: MouseEvent) => {
+      if (zoomSliderRef.current && !zoomSliderRef.current.contains(e.target as Node)) {
+        setShowZoomSlider(false);
+      }
+    };
+    document.addEventListener('mousedown', handleClickOutside);
+    return () => document.removeEventListener('mousedown', handleClickOutside);
+  }, [showZoomSlider]);
+
   return (
     <div className="piano-roll-toolbar">
-      <div className="toolbar-left">
+      {showMidiControls && (
-        {/* Left section with mode and chord guide dropdowns */}
+        <div className="toolbar-left">
-        <KGDropdown
+          <button
-          options={Object.entries(KGCore.FUNCTIONAL_CHORDS_DATA).map(([id, data]) => ({ label: data.name, value: id }))}
+            className={`tool-button ${activeTool === 'pointer' ? 'active' : ''}`}
-          value={selectedMode}
+            onClick={() => onToolSelect('pointer')}
-          onChange={(value) => onModeChange(value)}
+            title="Pointer Tool"
-          label="Mode"
+          >
-          buttonClassName="mode-dropdown"
+            <FaMousePointer />
-          showValueAsLabel={true}
+          </button>
-        />
+          <button
-        <KGDropdown
+            className={`tool-button ${activeTool === 'pencil' ? 'active' : ''}`}
-          options={[
+            onClick={() => onToolSelect('pencil')}
-            { label: 'Guide: Disabled', value: 'N' },
+            title="Pencil Tool"
-            { label: 'Chord Guide: T', value: 'T' },
+          >
-            { label: 'Chord Guide: S', value: 'S' }, 
+            <FaPencilAlt />
-            { label: 'Chord Guide: D', value: 'D' }
+          </button>
-          ]}
+          <KGDropdown
-          value={chordGuide}
+            options={Object.entries(KGCore.FUNCTIONAL_CHORDS_DATA).map(([id, data]) => ({ label: data.name, value: id }))}
-          onChange={(value) => onChordGuideChange(value)}
+            value={selectedMode}
-          label="Chord"
+            onChange={(value) => onModeChange(value)}
-          buttonClassName="chord-guide-dropdown"
+            label="Mode"
-          showValueAsLabel={true}
+            buttonClassName="mode-dropdown"
-        />
+            showValueAsLabel={true}
-      </div>
+          />
-      
+          <KGDropdown
-      <div className="toolbar-center">
+            options={[
-        {/* Center section with pointer and pencil tools */}
+              { label: 'Guide: Disabled', value: 'N' },
-        <button 
+              { label: 'Chord Guide: T', value: 'T' },
-          className={`tool-button ${activeTool === 'pointer' ? 'active' : ''}`}
+              { label: 'Chord Guide: S', value: 'S' },
-          onClick={() => onToolSelect('pointer')}
+              { label: 'Chord Guide: D', value: 'D' }
-          title="Pointer Tool"
+            ]}
-        >
+            value={chordGuide}
-          <FaMousePointer />
+            onChange={(value) => onChordGuideChange(value)}
-        </button>
+            label="Chord"
-        <button 
+            buttonClassName="chord-guide-dropdown"
-          className={`tool-button ${activeTool === 'pencil' ? 'active' : ''}`}
+            showValueAsLabel={true}
-          onClick={() => onToolSelect('pencil')}
+          />
-          title="Pencil Tool"
+        </div>
-        >
+      )}
-          <FaPencilAlt />
-        </button>
-      </div>
 
       <div className="toolbar-right">
-        {/* Right section with quantization options */}
+        {showMidiControls && (
-        <KGDropdown
+          <>
-          options={KGPianoRollState.SNAP_OPTIONS}
+            <KGDropdown
-          value={snapping}
+              options={KGPianoRollState.SNAP_OPTIONS}
-          onChange={(value) => onSnappingSelect(value)}
+              value={snapping}
-          label="Snap"
+              onChange={(value) => onSnappingSelect(value)}
-          buttonClassName="snapping"
+              label="Snap"
-          showValueAsLabel={true}
+              buttonClassName="snapping"
-        />
+              showValueAsLabel={true}
+            />
+            <KGDropdown
+              options={KGPianoRollState.QUANT_POS_OPTIONS}
+              value={quantPosition}
+              onChange={(value) => onQuantSelect('position', value)}
+              label="Qua. Pos."
+              buttonClassName={`quant-position ${blinkButton === 'quant-position' ? 'button-blink' : ''}`}
+            />
+            <KGDropdown
+              options={KGPianoRollState.QUANT_LEN_OPTIONS}
+              value={quantLength}
+              onChange={(value) => onQuantSelect('length', value)}
+              label="Qua. Len."
+              buttonClassName={`quant-length ${blinkButton === 'quant-length' ? 'button-blink' : ''}`}
+            />
+          </>
+        )}
 
-        <KGDropdown
+        {showSpecControls && (
-          options={KGPianoRollState.QUANT_POS_OPTIONS}
+          <div className="spectrogram-toolbar-controls">
-          value={quantPosition}
+            <span className="spectrogram-control-label">Floor</span>
-          onChange={(value) => onQuantSelect('position', value)}
+            <input
-          label="Qua. Pos."
+              type="range"
-          buttonClassName={`quant-position ${blinkButton === 'quant-position' ? 'button-blink' : ''}`}
+              className="spectrogram-threshold-slider"
-        />
+              min={-50}
+              max={-5}
+              step={1}
+              value={thresholdDb}
+              onChange={e => onThresholdChange?.(parseInt(e.target.value))}
+              title={`Noise floor: ${thresholdDb} dB`}
+            />
+            <span className="spectrogram-threshold-value">{thresholdDb} dB</span>
+            <KGDropdown
+              options={POWER_OPTIONS}
+              value={power.toString()}
+              onChange={v => onPowerChange?.(parseFloat(v))}
+              label="Curve"
+              buttonClassName="curve-dropdown"
+              showValueAsLabel={true}
+            />
+          </div>
+        )}
 
-        <KGDropdown
+        <div className="quant-dropdown-container" ref={zoomSliderRef}>
-          options={KGPianoRollState.QUANT_LEN_OPTIONS}
+          <button
-          value={quantLength}
+            className="quant-button"
-          onChange={(value) => onQuantSelect('length', value)}
+            onClick={() => setShowZoomSlider(!showZoomSlider)}
-          label="Qua. Len."
+            title="Zoom"
-          buttonClassName={`quant-length ${blinkButton === 'quant-length' ? 'button-blink' : ''}`}
+          >
-        />
+            {zoom}x
+          </button>
+          {showZoomSlider && (
+            <div className="piano-roll-zoom-popup">
+              <input
+                type="range"
+                min="1"
+                max="8"
+                step="1"
+                value={zoom}
+                onChange={(e) => onZoomChange(parseInt(e.target.value))}
+              />
+              <span className="piano-roll-zoom-value">{zoom}x</span>
+            </div>
+          )}
+        </div>
       </div>
     </div>
   );

src/components/piano-roll/SpectrogramCanvas.tsx

@@ -0,0 +1,260 @@
+import React, { useCallback, useEffect, useRef, useState } from 'react';
+import * as Tone from 'tone';
+import { KGAudioRegion } from '../../core/region/KGAudioRegion';
+import { KGAudioInterface } from '../../core/audio-interface/KGAudioInterface';
+import { KGAudioFileStorage } from '../../core/io/KGAudioFileStorage';
+import type { SpectrogramRequest, SpectrogramResult } from '../../workers/spectrogramWorker';
+
+interface SpectrogramCanvasProps {
+  audioRegion: KGAudioRegion;
+  trackId: string;
+  projectName: string;
+  bpm: number;
+  thresholdDb: number;
+  power: number;
+  zoom: number;
+  onLoadingChange?: (loading: boolean) => void;
+}
+
+const PITCH_BINS = 128;
+const HOP_SIZE = 1024;
+
+// Piecewise-linear RGB colormap: black → dark blue → blue → purple → red → orange → yellow
+// Hue rotates 240°→300°→0°→60°, bypassing green entirely.
+const COLORMAP_STOPS: Array<[number, [number, number, number]]> = [
+  [0.00, [  0,   0,   0]],
+  [0.15, [  0,   0, 180]],
+  [0.35, [  0,  60, 255]],
+  [0.55, [180,   0, 120]],
+  [0.70, [255,   0,   0]],
+  [0.85, [255, 140,   0]],
+  [1.00, [255, 255,   0]],
+];
+
+function hotColormap(v: number): [number, number, number] {
+  v = Math.max(0, Math.min(1, v));
+  for (let i = 0; i < COLORMAP_STOPS.length - 1; i++) {
+    const [t0, c0] = COLORMAP_STOPS[i];
+    const [t1, c1] = COLORMAP_STOPS[i + 1];
+    if (v <= t1) {
+      const t = (v - t0) / (t1 - t0);
+      return [
+        Math.round(c0[0] + t * (c1[0] - c0[0])),
+        Math.round(c0[1] + t * (c1[1] - c0[1])),
+        Math.round(c0[2] + t * (c1[2] - c0[2])),
+      ];
+    }
+  }
+  return COLORMAP_STOPS[COLORMAP_STOPS.length - 1][1];
+}
+
+const SpectrogramCanvas: React.FC<SpectrogramCanvasProps> = ({
+  audioRegion,
+  trackId,
+  projectName,
+  bpm,
+  thresholdDb,
+  power,
+  zoom,
+  onLoadingChange,
+}) => {
+  const canvasRef = useRef<HTMLCanvasElement | null>(null);
+  const [loading, setLoading] = useState(true);
+  const workerRef = useRef<Worker | null>(null);
+
+  // Cache the raw linear result so threshold/power changes re-render without re-running FFT
+  const rawResultRef = useRef<SpectrogramResult | null>(null);
+  const sampleRateRef = useRef<number>(44100);
+  const regionDurationRef = useRef<number>(0);
+  // Natural (1x) canvas pixel width — set after each draw, used to apply zoom as CSS stretch
+  const naturalWidthRef = useRef<number>(0);
+  // Always-current zoom without making it a renderSpectrogram dependency
+  const zoomRef = useRef(zoom);
+  useEffect(() => { zoomRef.current = zoom; }, [zoom]);
+
+  useEffect(() => { onLoadingChange?.(loading); }, [loading, onLoadingChange]);
+
+  const renderSpectrogram = useCallback((
+    result: SpectrogramResult,
+    sampleRate: number,
+    regionDurationSeconds: number,
+    thresholdDb: number,
+    power: number,
+  ) => {
+    const canvas = canvasRef.current;
+    if (!canvas) return;
+    const ctx = canvas.getContext('2d');
+    if (!ctx) return;
+
+    const noteHeight =
+      parseInt(getComputedStyle(document.documentElement).getPropertyValue('--region-piano-key-height')) || 20;
+
+    const totalBeats = (regionDurationSeconds * bpm) / 60;
+    // Always draw at 1x resolution; zoom is applied as CSS width stretch
+    const canvasWidth = Math.ceil(totalBeats * 40);
+    const canvasHeight = PITCH_BINS * noteHeight;
+
+    // Convert dB threshold to linear: values below this → black
+    const linearThreshold = Math.pow(10, thresholdDb / 20);
+
+    // 1. Paint at natural STFT resolution onto an offscreen canvas (timeSteps × 128).
+    //    Row i = pitchIndex i = pitch (107 − i). Apply threshold then power curve.
+    const offscreen = document.createElement('canvas');
+    offscreen.width = result.timeSteps;
+    offscreen.height = PITCH_BINS;
+    const offCtx = offscreen.getContext('2d');
+    if (!offCtx) return;
+
+    const imgData = offCtx.createImageData(result.timeSteps, PITCH_BINS);
+    const pixels = imgData.data;
+
+    for (let row = 0; row < PITCH_BINS; row++) {
+      const pitch = 107 - row;
+      for (let col = 0; col < result.timeSteps; col++) {
+        const idx = (row * result.timeSteps + col) * 4;
+        pixels[idx + 3] = 255; // always opaque
+
+        if (pitch < 12 || pitch > 107) continue; // outside range → black
+
+        const raw = result.data[col * PITCH_BINS + pitch];
+
+        // Hard threshold: values below noise floor → 0 (black)
+        // Re-scale surviving range to [0,1] then apply power curve
+        const gated = raw < linearThreshold
+          ? 0
+          : Math.pow((raw - linearThreshold) / (1 - linearThreshold), power);
+
+        if (gated <= 0) continue; // stays black
+
+        const [r, g, b] = hotColormap(gated);
+        pixels[idx]     = r;
+        pixels[idx + 1] = g;
+        pixels[idx + 2] = b;
+      }
+    }
+
+    offCtx.putImageData(imgData, 0, 0);
+
+    // 2. Stretch onto the full canvas — browser bilinear filter smooths between bins.
+    canvas.width = canvasWidth;
+    canvas.height = canvasHeight;
+    ctx.imageSmoothingEnabled = true;
+    ctx.imageSmoothingQuality = 'high';
+    ctx.drawImage(offscreen, 0, 0, canvasWidth, canvasHeight);
+
+    // Store natural width and apply current zoom as CSS stretch (no pixel recompute on zoom)
+    naturalWidthRef.current = canvasWidth;
+    canvas.style.width = `${canvasWidth * zoomRef.current}px`;
+    canvas.style.height = `${canvasHeight}px`;
+  }, [bpm]);
+
+  // Re-render without re-running the worker when threshold or power changes
+  useEffect(() => {
+    if (rawResultRef.current) {
+      renderSpectrogram(
+        rawResultRef.current,
+        sampleRateRef.current,
+        regionDurationRef.current,
+        thresholdDb,
+        power,
+      );
+    }
+  }, [thresholdDb, power, renderSpectrogram]);
+
+  // Zoom changes: stretch width only, pin height to canvas pixel height
+  useEffect(() => {
+    if (canvasRef.current && naturalWidthRef.current > 0) {
+      canvasRef.current.style.width = `${naturalWidthRef.current * zoom}px`;
+      canvasRef.current.style.height = `${canvasRef.current.height}px`;
+    }
+  }, [zoom]);
+
+  // Load audio + run worker when the audio region itself changes
+  useEffect(() => {
+    let cancelled = false;
+
+    const compute = async () => {
+      setLoading(true);
+      workerRef.current?.terminate();
+      workerRef.current = null;
+
+      try {
+        let audioBuffer: AudioBuffer | undefined = KGAudioInterface.instance().getAudioBuffer(
+          trackId,
+          audioRegion.getAudioFileId()
+        );
+
+        if (!audioBuffer) {
+          const arrayBuffer = await KGAudioFileStorage.loadAudioFile(
+            projectName,
+            audioRegion.getAudioFileId()
+          );
+          if (cancelled) return;
+          const actx = Tone.getContext().rawContext as AudioContext;
+          audioBuffer = await actx.decodeAudioData(arrayBuffer);
+        }
+
+        if (cancelled) return;
+
+        const pcm = audioBuffer.getChannelData(0);
+        const sampleRate = audioBuffer.sampleRate;
+        const regionDurationSeconds = (audioRegion.getLength() * 60) / bpm;
+
+        const worker = new Worker(
+          new URL('../../workers/spectrogramWorker.ts', import.meta.url),
+          { type: 'module' }
+        );
+        workerRef.current = worker;
+
+        worker.onmessage = (e: MessageEvent<SpectrogramResult>) => {
+          if (cancelled) { worker.terminate(); return; }
+          rawResultRef.current = e.data;
+          sampleRateRef.current = sampleRate;
+          regionDurationRef.current = regionDurationSeconds;
+          renderSpectrogram(e.data, sampleRate, regionDurationSeconds, thresholdDb, power);
+          setLoading(false);
+          worker.terminate();
+          workerRef.current = null;
+        };
+
+        const request: SpectrogramRequest = {
+          pcm: pcm.slice(0) as Float32Array,
+          sampleRate,
+          clipStartOffsetSeconds: audioRegion.getClipStartOffsetSeconds(),
+          regionDurationSeconds,
+          bpm,
+        };
+        worker.postMessage(request, [request.pcm.buffer]);
+      } catch (err) {
+        if (!cancelled) {
+          console.error('SpectrogramCanvas: failed to compute spectrogram', err);
+          setLoading(false);
+        }
+      }
+    };
+
+    compute();
+
+    return () => {
+      cancelled = true;
+      workerRef.current?.terminate();
+      workerRef.current = null;
+    };
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [audioRegion, trackId, projectName, bpm]);
+
+  return (
+    <canvas
+      ref={canvasRef}
+      style={{
+        position: 'absolute',
+        top: 0,
+        left: 0,
+        zIndex: 0,
+        pointerEvents: 'none',
+      }}
+    />
+  );
+};
+
+export default SpectrogramCanvas;

src/components/track/Region.css

@@ -97,11 +97,23 @@
   background-color: #5a9b6a;
 }
 
-/* Region pencil trigger inside content */
+/* Left-side button cluster inside region-content */
-.region-pencil-btn {
+.region-left-buttons {
   position: absolute;
   top: 4px;
   left: 4px;
+  display: flex;
+  flex-direction: row;
+  align-items: center;
+  gap: 2px;
+  z-index: 2;
+}
+
+/* Shared style for all region content buttons */
+.region-pencil-btn,
+.region-waveform-btn,
+.region-spectrogram-btn,
+.region-hybrid-btn {
   background: rgba(0, 0, 0, 0.25);
   color: #fff;
   border: 1px solid rgba(255, 255, 255, 0.2);
@@ -109,16 +121,63 @@
   padding: 2px;
   margin: 0;
   cursor: pointer;
-  z-index: 2;
   display: inline-flex;
   align-items: center;
   justify-content: center;
 }
 
-.region-pencil-btn:hover {
+.region-pencil-btn:hover,
+.region-spectrogram-btn:hover,
+.region-hybrid-btn:hover {
   background: rgba(0, 0, 0, 0.35);
 }
 
+.region-waveform-btn {
+  display: none;
+}
+
+.region-waveform-btn:hover {
+  background: rgba(0, 0, 0, 0.35);
+}
+
+/* Fine-move widget: sits inline in the left button cluster */
+.region-fine-move-widget {
+  display: flex;
+  flex-direction: row;
+  align-items: center;
+  gap: 2px;
+}
+
+.region-fine-move-btn {
+  background: rgba(0, 0, 0, 0.25);
+  color: #fff;
+  border: 1px solid rgba(255, 255, 255, 0.2);
+  border-radius: 3px;
+  padding: 2px;
+  margin: 0;
+  cursor: ew-resize;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  flex-shrink: 0;
+}
+
+.region-fine-move-btn:hover {
+  background: rgba(0, 0, 0, 0.35);
+}
+
+.region-fine-move-label {
+  background: rgba(0, 0, 0, 0.25);
+  color: #fff;
+  border: 1px solid rgba(255, 255, 255, 0.2);
+  border-radius: 3px;
+  padding: 2px 4px;
+  font-size: 10px;
+  white-space: nowrap;
+  line-height: 1;
+  user-select: none;
+}
+
 /* Instrument dropdown specific styles */
 .instrument-dropdown .quant-dropdown {
   min-width: 80px;

src/components/track/RegionItem.test.tsx

@@ -0,0 +1,97 @@
+import React from 'react';
+import { describe, it, expect, beforeAll, beforeEach, vi } from 'vitest';
+import { render, fireEvent } from '@testing-library/react';
+import RegionItem from './RegionItem';
+import { KGMidiRegion } from '../../core/region/KGMidiRegion';
+import { KGMainContentState } from '../../core/state/KGMainContentState';
+
+vi.mock('../../stores/projectStore', () => ({
+  useProjectStore: () => ({
+    selectedRegionIds: [],
+    timeSignature: { numerator: 4, denominator: 4 },
+    bpm: 120,
+  }),
+}));
+
+describe('RegionItem', () => {
+  beforeAll(() => {
+    Object.defineProperty(HTMLCanvasElement.prototype, 'getContext', {
+      value: vi.fn(() => ({
+        clearRect: vi.fn(),
+        fillRect: vi.fn(),
+      })),
+    });
+
+    class ResizeObserverMock {
+      observe() {}
+      unobserve() {}
+      disconnect() {}
+    }
+
+    vi.stubGlobal('ResizeObserver', ResizeObserverMock);
+  });
+
+  beforeEach(() => {
+    KGMainContentState.instance().setActiveTool('pointer');
+  });
+
+  const renderRegion = (props: Partial<React.ComponentProps<typeof RegionItem>> = {}) => {
+    const midiRegion = new KGMidiRegion('midi-1', 'track-1', 0, 'Test Region', 0, 4);
+
+    return render(
+      <RegionItem
+        id="midi-1"
+        name="Test Region"
+        style={{ left: '0px', width: '120px', position: 'absolute' }}
+        onClick={vi.fn()}
+        onDragStart={vi.fn()}
+        onDrag={vi.fn()}
+        onDragEnd={vi.fn()}
+        midiRegion={midiRegion}
+        {...props}
+      />
+    );
+  };
+
+  it('treats small pointer jitter as a click', () => {
+    const onClick = vi.fn();
+    const onDragStart = vi.fn();
+    const onDrag = vi.fn();
+    const onDragEnd = vi.fn();
+
+    const { container } = renderRegion({ onClick, onDragStart, onDrag, onDragEnd });
+    const region = container.querySelector('.track-region');
+
+    expect(region).toBeTruthy();
+
+    fireEvent.mouseDown(region!, { clientX: 100, clientY: 100 });
+    fireEvent.mouseMove(document, { clientX: 102, clientY: 102 });
+    fireEvent.mouseUp(document, { clientX: 102, clientY: 102 });
+
+    expect(onClick).toHaveBeenCalledWith('midi-1');
+    expect(onDragStart).not.toHaveBeenCalled();
+    expect(onDrag).not.toHaveBeenCalled();
+    expect(onDragEnd).not.toHaveBeenCalled();
+  });
+
+  it('starts a drag after crossing the movement threshold', () => {
+    const onClick = vi.fn();
+    const onDragStart = vi.fn();
+    const onDrag = vi.fn();
+    const onDragEnd = vi.fn();
+
+    const { container } = renderRegion({ onClick, onDragStart, onDrag, onDragEnd });
+    const region = container.querySelector('.track-region');
+
+    expect(region).toBeTruthy();
+
+    fireEvent.mouseDown(region!, { clientX: 100, clientY: 100 });
+    fireEvent.mouseMove(document, { clientX: 110, clientY: 100 });
+    fireEvent.mouseUp(document, { clientX: 110, clientY: 100 });
+
+    expect(onClick).not.toHaveBeenCalled();
+    expect(onDragStart).toHaveBeenCalledWith('midi-1', 100, 100);
+    expect(onDrag).toHaveBeenCalledWith('midi-1', 10, 0);
+    expect(onDragEnd).toHaveBeenCalledWith('midi-1');
+  });
+});

src/components/track/RegionItem.tsx

@@ -1,6 +1,7 @@
 import React, { useState, useRef, useEffect } from 'react';
 import './Region.css';
-import { FaPencilAlt } from 'react-icons/fa';
+import { FaPencilAlt, FaPlus } from 'react-icons/fa';
+import { MdGraphicEq, MdSwapHoriz } from 'react-icons/md';
 import type { ResizeAction } from '../interfaces';
 import { REGION_CONSTANTS, DEBUG_MODE } from '../../constants';
 import { KGMidiRegion } from '../../core/region/KGMidiRegion';
@@ -8,6 +9,8 @@ import { KGAudioRegion } from '../../core/region/KGAudioRegion';
 import { useProjectStore } from '../../stores/projectStore';
 import { KGMainContentState } from '../../core/state/KGMainContentState';
 
+const DRAG_START_THRESHOLD_PX = 4;
+
 interface RegionItemProps {
   id: string;
   name: string;
@@ -27,6 +30,13 @@ interface RegionItemProps {
   onClick?: (regionId: string) => void;
   // Explicit open piano roll action from header pencil icon
   onOpenPianoRoll?: (regionId: string) => void;
+  // Open spectrogram viewer for audio regions
+  onOpenSpectrogram?: (regionId: string) => void;
+  // Enter hybrid mode (show + when piano roll is open with the opposite region type selected)
+  showHybridButton?: boolean;
+  onOpenHybrid?: (regionId: string) => void;
+  // Fine-move end callback — passes raw (unscaled) mouse pixel delta
+  onFineMoveEnd?: (regionId: string, rawPixelDelta: number) => void;
   // MIDI region data for rendering notes
   midiRegion?: KGMidiRegion;
   // Audio region data for rendering waveform
@@ -49,6 +59,10 @@ const RegionItem: React.FC<RegionItemProps> = ({
   onDragEnd,
   onClick,
   onOpenPianoRoll,
+  onOpenSpectrogram,
+  showHybridButton,
+  onOpenHybrid,
+  onFineMoveEnd,
   midiRegion,
   audioRegion,
   audioBuffer
@@ -60,11 +74,19 @@ const RegionItem: React.FC<RegionItemProps> = ({
   const [resizeEdge, setResizeEdge] = useState<ResizeAction>('none');
   const [isResizing, setIsResizing] = useState(false);
   const [isDragging, setIsDragging] = useState(false);
-  const initialMousePosRef = useRef<{x: number, y: number}>({x: 0, y: 0});
+  const initialMousePosRef = useRef<{ x: number, y: number }>({ x: 0, y: 0 });
   // Use refs to track states for immediate access
   const isResizingRef = useRef<boolean>(false);
   const isDraggingRef = useRef<boolean>(false);
-  const hasMovedRef = useRef<boolean>(false);
+  const isPendingDragRef = useRef<boolean>(false);
+
+  // Fine-move state
+  const [isFineDragging, setIsFineDragging] = useState(false);
+  const [fineDeltaDisplay, setFineDeltaDisplay] = useState('+0.00');
+  const [fineTranslateX, setFineTranslateX] = useState(0);
+  const isFineDraggingRef = useRef(false);
+  const fineMouseStartXRef = useRef(0);
+  const fineRawDeltaRef = useRef(0);
 
   // Canvas ref for note visualization
   const canvasRef = useRef<HTMLCanvasElement | null>(null);
@@ -382,7 +404,7 @@ const RegionItem: React.FC<RegionItemProps> = ({
     const activeTool = KGMainContentState.instance().getActiveTool();
     if (activeTool === 'pencil') {
       // Still allow click events to pass through for region selection
-      if (!hasMovedRef.current && onClick) {
+      if (onClick) {
         if (DEBUG_MODE.REGION_ITEM) {
           console.log(`REGION CLICKED (pencil mode): regionId=${id}`);
         }
@@ -395,7 +417,7 @@ const RegionItem: React.FC<RegionItemProps> = ({
     e.preventDefault();
 
     // Reset movement tracking
-    hasMovedRef.current = false;
+    isPendingDragRef.current = false;
 
     // Store initial mouse position
     initialMousePosRef.current = { x: e.clientX, y: e.clientY };
@@ -414,21 +436,12 @@ const RegionItem: React.FC<RegionItemProps> = ({
         onResizeStart(id, resizeEdge, e.clientX);
       }
     } else {
-      // Start dragging
+      // Wait for actual pointer movement before promoting this gesture to a drag.
       if (DEBUG_MODE.REGION_ITEM) {
-        console.log(`DRAG START: regionId=${id}`);
+        console.log(`PENDING REGION INTERACTION: regionId=${id}`);
       }
 
-      setIsDragging(true);
+      isPendingDragRef.current = true;
-      isDraggingRef.current = true;
-
-      // Change cursor to grabbing during drag
-      setCursor('grabbing');
-
-      // Call the onDragStart callback if provided
-      if (onDragStart) {
-        onDragStart(id, e.clientX, e.clientY);
-      }
     }
 
     // Add global event listeners for mouse move and up
@@ -438,9 +451,6 @@ const RegionItem: React.FC<RegionItemProps> = ({
 
   // Handle global mouse move for resize or drag
   const handleGlobalMouseMove = (e: MouseEvent) => {
-    // Set the hasMovedRef to true as soon as there's movement
-    hasMovedRef.current = true;
-
     if (isResizingRef.current) {
       // Handle resize
       if (DEBUG_MODE.REGION_ITEM) {
@@ -454,16 +464,35 @@ const RegionItem: React.FC<RegionItemProps> = ({
       if (onResize) {
         onResize(id, resizeEdge, deltaX);
       }
-    } else if (isDraggingRef.current) {
+    } else if (isDraggingRef.current || isPendingDragRef.current) {
+      const deltaX = e.clientX - initialMousePosRef.current.x;
+      const deltaY = e.clientY - initialMousePosRef.current.y;
+      const movedEnough = Math.hypot(deltaX, deltaY) >= DRAG_START_THRESHOLD_PX;
+
+      if (!isDraggingRef.current) {
+        if (!movedEnough) {
+          return;
+        }
+
+        if (DEBUG_MODE.REGION_ITEM) {
+          console.log(`DRAG START: regionId=${id}`);
+        }
+
+        isPendingDragRef.current = false;
+        setIsDragging(true);
+        isDraggingRef.current = true;
+        setCursor('grabbing');
+
+        if (onDragStart) {
+          onDragStart(id, initialMousePosRef.current.x, initialMousePosRef.current.y);
+        }
+      }
+
       // Handle drag
       if (DEBUG_MODE.REGION_ITEM) {
         console.log(`DRAG MOVE: regionId=${id}, trackIndex=${trackIndex}`);
       }
 
-      // Calculate delta from initial position
-      const deltaX = e.clientX - initialMousePosRef.current.x;
-      const deltaY = e.clientY - initialMousePosRef.current.y;
-
       // Call the onDrag callback if provided
       if (onDrag) {
         onDrag(id, deltaX, deltaY);
@@ -502,26 +531,62 @@ const RegionItem: React.FC<RegionItemProps> = ({
       if (onDragEnd) {
         onDragEnd(id);
       }
-
+    } else if (isPendingDragRef.current && onClick) {
-      // If there was no movement, treat it as a click
+      if (DEBUG_MODE.REGION_ITEM) {
-      if (!hasMovedRef.current && onClick) {
+        console.log(`REGION CLICKED: regionId=${id}`);
-        if (DEBUG_MODE.REGION_ITEM) {
-          console.log(`REGION CLICKED: regionId=${id}`);
-        }
-        onClick(id);
       }
+      onClick(id);
     }
 
+    isPendingDragRef.current = false;
+
     // Remove global event listeners
     document.removeEventListener('mousemove', handleGlobalMouseMove);
     document.removeEventListener('mouseup', handleGlobalMouseUp);
   };
 
+  // Fine-move handlers
+  const handleFineMoveGlobalMouseMove = (e: MouseEvent) => {
+    if (!isFineDraggingRef.current) return;
+    const rawDelta = e.clientX - fineMouseStartXRef.current;
+    fineRawDeltaRef.current = rawDelta;
+    const scaledDelta = rawDelta * REGION_CONSTANTS.FINE_MOVE_SPEED_RATIO;
+    setFineTranslateX(scaledDelta);
+    setFineDeltaDisplay(scaledDelta >= 0 ? `+${scaledDelta.toFixed(2)}` : `${scaledDelta.toFixed(2)}`);
+  };
+
+  const handleFineMoveGlobalMouseUp = () => {
+    if (!isFineDraggingRef.current) return;
+    isFineDraggingRef.current = false;
+    setIsFineDragging(false);
+    setFineTranslateX(0);
+    document.removeEventListener('mousemove', handleFineMoveGlobalMouseMove);
+    document.removeEventListener('mouseup', handleFineMoveGlobalMouseUp);
+    if (fineRawDeltaRef.current !== 0 && onFineMoveEnd) {
+      onFineMoveEnd(id, fineRawDeltaRef.current);
+    }
+  };
+
+  const handleFineMoveMouseDown = (e: React.MouseEvent<HTMLButtonElement>) => {
+    e.preventDefault();
+    e.stopPropagation();
+    if (isFineDraggingRef.current) return;
+    fineMouseStartXRef.current = e.clientX;
+    fineRawDeltaRef.current = 0;
+    isFineDraggingRef.current = true;
+    setIsFineDragging(true);
+    setFineDeltaDisplay('+0.00');
+    document.addEventListener('mousemove', handleFineMoveGlobalMouseMove);
+    document.addEventListener('mouseup', handleFineMoveGlobalMouseUp);
+  };
+
   // Clean up event listeners on unmount
   useEffect(() => {
     return () => {
       document.removeEventListener('mousemove', handleGlobalMouseMove);
       document.removeEventListener('mouseup', handleGlobalMouseUp);
+      document.removeEventListener('mousemove', handleFineMoveGlobalMouseMove);
+      document.removeEventListener('mouseup', handleFineMoveGlobalMouseUp);
     };
   }, []);
 
@@ -538,7 +603,7 @@ const RegionItem: React.FC<RegionItemProps> = ({
     <div
       key={id}
       className={`track-region ${isDragging ? 'dragging' : ''} ${isSelected ? 'selected' : ''} ${audioRegion ? 'audio-region' : ''}`}
-      style={{ ...style, cursor }}
+      style={{ ...style, cursor, ...(isFineDragging ? { transform: `translateX(${fineTranslateX}px)`, zIndex: 100 } : {}) }}
       onMouseMove={handleMouseMove}
       onMouseLeave={handleMouseLeave}
       onMouseDown={handleMouseDown}
@@ -551,31 +616,108 @@ const RegionItem: React.FC<RegionItemProps> = ({
         {name}
       </div>
       <div className={`region-content${audioRegion ? ' audio-region-content' : ''}`} ref={regionContentRef}>
-        {!audioRegion && (
+        <div className="region-left-buttons">
-          <button
+          {!audioRegion && (
-            className="region-pencil-btn"
+            <button
-            title="Edit notes"
+              className="region-pencil-btn"
-            onMouseDown={(e) => {
+              title="Edit notes"
-              e.preventDefault();
+              onMouseDown={(e) => {
-              e.stopPropagation();
+                e.preventDefault();
-            }}
+                e.stopPropagation();
-            onClick={(e) => {
+              }}
-              e.preventDefault();
+              onClick={(e) => {
-              e.stopPropagation();
+                e.preventDefault();
-              if (DEBUG_MODE.REGION_ITEM) {
+                e.stopPropagation();
-                console.log(`Pencil clicked: open piano roll for region ${id}`);
+                if (DEBUG_MODE.REGION_ITEM) {
-              }
+                  console.log(`Pencil clicked: open piano roll for region ${id}`);
-              if (onOpenPianoRoll) {
+                }
-                onOpenPianoRoll(id);
+                if (onOpenPianoRoll) {
-              } else if (onClick) {
+                  onOpenPianoRoll(id);
-                onClick(id);
+                } else if (onClick) {
-              }
+                  onClick(id);
-            }}
+                }
-            aria-label="Open piano roll"
+              }}
-          >
+              aria-label="Open piano roll"
-            <FaPencilAlt size={10} />
+            >
-          </button>
+              <FaPencilAlt size={10} />
-        )}
+            </button>
+          )}
+          {audioRegion && (
+            <button
+              className="region-waveform-btn"
+              title="View waveform"
+              onMouseDown={(e) => {
+                e.preventDefault();
+                e.stopPropagation();
+              }}
+              onClick={(e) => {
+                e.preventDefault();
+                e.stopPropagation();
+              }}
+              aria-label="View waveform"
+            >
+              <MdGraphicEq size={10} />
+            </button>
+          )}
+          {audioRegion && (
+            <button
+              className="region-spectrogram-btn"
+              title="View melodic spectrogram"
+              onMouseDown={(e) => {
+                e.preventDefault();
+                e.stopPropagation();
+              }}
+              onClick={(e) => {
+                e.preventDefault();
+                e.stopPropagation();
+                if (onOpenSpectrogram) {
+                  onOpenSpectrogram(id);
+                }
+              }}
+              aria-label="View spectrogram"
+            >
+              <svg width="10" height="10" viewBox="0 0 10 10" fill="currentColor">
+                <rect x="3" y="0.5" width="6.5" height="2.5" rx="0.4"/>
+                <rect x="1.5" y="3.75" width="6.5" height="2.5" rx="0.4"/>
+                <rect x="0" y="7" width="6.5" height="2.5" rx="0.4"/>
+              </svg>
+            </button>
+          )}
+          {showHybridButton && (
+            <button
+              className="region-hybrid-btn"
+              title="Open in hybrid mode"
+              onMouseDown={(e) => {
+                e.preventDefault();
+                e.stopPropagation();
+              }}
+              onClick={(e) => {
+                e.preventDefault();
+                e.stopPropagation();
+                if (onOpenHybrid) {
+                  onOpenHybrid(id);
+                }
+              }}
+              aria-label="Open hybrid mode"
+            >
+              <FaPlus size={10} />
+            </button>
+          )}
+          <div className="region-fine-move-widget">
+            <button
+              className="region-fine-move-btn"
+              title="Fine move"
+              onMouseDown={handleFineMoveMouseDown}
+              onClick={(e) => { e.preventDefault(); e.stopPropagation(); }}
+              aria-label="Fine move region"
+            >
+              <MdSwapHoriz size={10} />
+            </button>
+            {isFineDragging && (
+              <span className="region-fine-move-label">{fineDeltaDisplay}</span>
+            )}
+          </div>
+        </div>
         <canvas ref={canvasRef} />
       </div>
     </div>

src/components/track/Track.css

@@ -49,7 +49,7 @@
 }
 
 .track-info {
-  width: 200px;
+  width: var(--track-info-panel-width);
   height: 120px;
   padding: 15px 5px 15px 15px;
   background-color: #2d2d2d;

src/components/track/TrackGridItem.tsx

@@ -24,8 +24,13 @@ interface TrackGridItemProps {
   onRegionResizeEnd?: (regionId: string, finalBarNumber: number, finalLength: number) => void;
   onRegionDrag?: (regionId: string, newBarNumber: number, newTrackIndex: number) => void;
   onRegionDragEnd?: (regionId: string, finalBarNumber: number, finalTrackIndex: number) => void;
+  onRegionFineMoveEnd?: (regionId: string, deltaInBars: number) => void;
   onRegionClick?: (regionId: string) => void;
   onOpenPianoRoll?: (regionId: string) => void;
+  onOpenSpectrogram?: (regionId: string) => void;
+  showHybridButtonForAudio?: boolean;
+  showHybridButtonForMidi?: boolean;
+  onOpenHybrid?: (regionId: string) => void;
   allTracks?: KGTrack[]; // Added to access all tracks for drag operations
   onKGOneClipDrop?: (e: React.DragEvent<HTMLDivElement>, trackIndex: number) => void;
 }
@@ -45,8 +50,13 @@ const TrackGridItem: React.FC<TrackGridItemProps> = ({
   onRegionResizeEnd,
   onRegionDrag,
   onRegionDragEnd,
+  onRegionFineMoveEnd,
   onRegionClick,
   onOpenPianoRoll,
+  onOpenSpectrogram,
+  showHybridButtonForAudio,
+  showHybridButtonForMidi,
+  onOpenHybrid,
   allTracks,
   onKGOneClipDrop,
 }) => {
@@ -484,12 +494,27 @@ const TrackGridItem: React.FC<TrackGridItemProps> = ({
     currentDragTop.current = null;
     currentDragRegion.current = null;
     
+    if (finalBarNumber === region.barNumber && finalTrackIndex === region.trackIndex) {
+      if (DEBUG_MODE.TRACK_GRID_ITEM) {
+        console.log(`Skipping no-op drag update for region ${regionId}`);
+      }
+      return;
+    }
+
     // Notify parent about drag end with final values
     if (onRegionDragEnd) {
       onRegionDragEnd(regionId, finalBarNumber, finalTrackIndex);
     }
   };
 
+  // Handle fine-move end — convert raw pixel delta to delta in bars and pass up
+  const handleRegionFineMoveEnd = (regionId: string, rawPixelDelta: number) => {
+    const barWidth = containerWidth / maxBars;
+    if (barWidth <= 0) return;
+    const deltaInBars = (rawPixelDelta * REGION_CONSTANTS.FINE_MOVE_SPEED_RATIO) / barWidth;
+    onRegionFineMoveEnd?.(regionId, deltaInBars);
+  };
+
   // Handle region click
   const handleRegionClick = (regionId: string) => {
     if (DEBUG_MODE.TRACK_GRID_ITEM) {
@@ -555,6 +580,7 @@ const TrackGridItem: React.FC<TrackGridItemProps> = ({
             onDragStart={handleRegionDragStart}
             onDrag={handleRegionDrag}
             onDragEnd={handleRegionDragEnd}
+            onFineMoveEnd={handleRegionFineMoveEnd}
             // Keep onClick for selection-only logic if needed by parent
             onClick={handleRegionClick}
             // New explicit pencil action — disabled for audio regions
@@ -566,6 +592,11 @@ const TrackGridItem: React.FC<TrackGridItemProps> = ({
                 onRegionClick(regionId);
               }
             }}
+            onOpenSpectrogram={audioRegion ? (regionId) => {
+              onOpenSpectrogram?.(regionId);
+            } : undefined}
+            showHybridButton={audioRegion ? showHybridButtonForAudio : showHybridButtonForMidi}
+            onOpenHybrid={onOpenHybrid}
             midiRegion={midiRegion}
             audioRegion={audioRegion}
             audioBuffer={audioBuffer}

src/components/track/TrackGridPanel.tsx

@@ -30,6 +30,10 @@ interface TrackGridPanelProps {
   onRegionUpdated?: (regionId: string, updates: Partial<RegionUI>, expectedModelUpdates?: { startBeat: number, length: number }) => void;
   onRegionClick?: (regionId: string) => void;
   onOpenPianoRoll?: (regionId: string) => void;
+  onOpenSpectrogram?: (regionId: string) => void;
+  showHybridButtonForAudio?: boolean;
+  showHybridButtonForMidi?: boolean;
+  onOpenHybrid?: (regionId: string) => void;
   onExternalDropComplete?: (trackIndex: number, regionUI: RegionUI) => void;
 }
 
@@ -46,6 +50,10 @@ const TrackGridPanel: React.FC<TrackGridPanelProps> = ({
   onRegionUpdated,
   onRegionClick,
   onOpenPianoRoll,
+  onOpenSpectrogram,
+  showHybridButtonForAudio,
+  showHybridButtonForMidi,
+  onOpenHybrid,
   onExternalDropComplete,
 }) => {
   const gridContainerRef = useRef<HTMLDivElement>(null);
@@ -379,6 +387,13 @@ const TrackGridPanel: React.FC<TrackGridPanelProps> = ({
     const region = regions.find(r => r.id === regionId);
     if (!region) return;
 
+    if (finalBarNumber === region.barNumber && finalTrackIndex === region.trackIndex) {
+      if (DEBUG_MODE.TRACK_GRID_PANEL) {
+        console.log(`Skipping no-op move for region ${regionId}`);
+      }
+      return;
+    }
+    
     // Get the target track
     const targetTrack = tracks[finalTrackIndex];
     if (!targetTrack) return;
@@ -458,6 +473,44 @@ const TrackGridPanel: React.FC<TrackGridPanelProps> = ({
     }
   };
 
+  // Handle fine-move end — execute MoveRegionCommand with float-precision beat position
+  const handleRegionFineMoveEnd = (regionId: string, deltaInBars: number) => {
+    const region = regions.find(r => r.id === regionId);
+    if (!region) return;
+    const track = tracks.find(t => t.getId().toString() === region.trackId);
+    if (!track) return;
+    const coreRegion = track.getRegions().find(r => r.getId() === regionId);
+    if (!coreRegion) return;
+
+    const beatsPerBar = timeSignature.numerator;
+    const newStartFromBeat = Math.max(0, coreRegion.getStartFromBeat() + deltaInBars * beatsPerBar);
+    if (newStartFromBeat === coreRegion.getStartFromBeat()) return;
+
+    try {
+      // Use constructor directly (NOT fromBarCoordinates) to preserve float precision
+      const command = new MoveRegionCommand(
+        regionId,
+        newStartFromBeat,
+        track.getId().toString(),
+        region.trackIndex
+      );
+      KGCore.instance().executeCommand(command);
+
+      if (DEBUG_MODE.TRACK_GRID_PANEL) {
+        console.log(`Fine-moved region ${regionId}: startFromBeat=${newStartFromBeat}`);
+      }
+
+      const newBarNumber = newStartFromBeat / beatsPerBar + 1;
+      onRegionUpdated?.(
+        regionId,
+        { barNumber: newBarNumber, trackId: region.trackId, trackIndex: region.trackIndex },
+        { startBeat: newStartFromBeat, length: coreRegion.getLength() }
+      );
+    } catch (error) {
+      console.error('Error executing fine-move:', error);
+    }
+  };
+
   // Handle region click
   const handleRegionClick = (regionId: string) => {
     if (DEBUG_MODE.TRACK_GRID_PANEL) {
@@ -649,8 +702,13 @@ const TrackGridPanel: React.FC<TrackGridPanelProps> = ({
           onRegionResizeEnd={handleRegionResizeEnd}
           onRegionDrag={handleRegionDrag}
           onRegionDragEnd={handleRegionDragEnd}
+          onRegionFineMoveEnd={handleRegionFineMoveEnd}
           onRegionClick={handleRegionClick}
           onOpenPianoRoll={onOpenPianoRoll}
+          onOpenSpectrogram={onOpenSpectrogram}
+          showHybridButtonForAudio={showHybridButtonForAudio}
+          showHybridButtonForMidi={showHybridButtonForMidi}
+          onOpenHybrid={onOpenHybrid}
           allTracks={tracks}
           onKGOneClipDrop={handleExternalDrop}
         />

src/constants/uiConstants.ts

@@ -28,6 +28,8 @@ export const REGION_CONSTANTS = {
   EDGE_THRESHOLD: 10,
   // Minimum region length in bars
   MIN_REGION_LENGTH: 1.0,
+  // Fine-move speed ratio: mouse pixels to region movement pixels
+  FINE_MOVE_SPEED_RATIO: 0.25,
 };
 
 // Piano roll related constants

src/core/project-upgrader/upgradeToV7.test.ts

@@ -41,10 +41,10 @@ describe('upgradeToV7', () => {
   });
 
   it('clamps values that exceed MAX_TRACK_VOLUME_DB', () => {
-    // linear > 1.0 would give positive dB; cap at +6
+    // linear > 1.0 gives positive dB but 2.0 is still below the +12 dB ceiling
     const project = makeProject([2.0]);
     upgradeToV7(project);
-    expect(project.getTracks()[0].getVolume()).toBe(AUDIO_INTERFACE_CONSTANTS.MAX_TRACK_VOLUME_DB);
+    expect(project.getTracks()[0].getVolume()).toBeCloseTo(20 * Math.log10(2.0), 5);
   });
 
   it('bumps project structure version to 7', () => {

src/core/track/KGMidiTrack.test.ts

@@ -348,7 +348,7 @@ describe('KGMidiTrack', () => {
 
       // Volume outside valid dB range is clamped
       track.setVolume(10);
-      expect(track.getVolume()).toBe(6);
+      expect(track.getVolume()).toBe(10);
 
       track.setVolume(-100);
       expect(track.getVolume()).toBe(-60);

src/stores/projectStore.test.ts

@@ -0,0 +1,78 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { act } from '@testing-library/react';
+import { KGMidiTrack } from '../core/track/KGMidiTrack';
+
+const mockProject = {
+  getTimeSignature: () => ({ numerator: 4, denominator: 4 }),
+  getMaxBars: () => 32,
+  getBarWidthMultiplier: () => 1,
+  getTracks: () => [new KGMidiTrack('Track 1', 0, 'acoustic_grand_piano')],
+  getBpm: () => 120,
+  getKeySignature: () => 'C major',
+  getName: () => 'Test Project',
+  getSelectedMode: () => 'major',
+  getIsLooping: () => false,
+  getLoopingRange: () => null,
+};
+
+const mockCore = {
+  getCurrentProject: () => mockProject,
+  setPlayheadUpdateCallback: vi.fn(),
+  setPlaybackStateChangeCallback: vi.fn(),
+  getSelectedItems: () => [],
+  onSelectionChanged: vi.fn(),
+  canUndo: () => false,
+  canRedo: () => false,
+  getUndoDescription: () => '',
+  getRedoDescription: () => '',
+  setOnCommandHistoryChanged: vi.fn(),
+  executeCommand: vi.fn(),
+  clearSelectedItems: vi.fn(),
+  getStatus: () => 'Ready',
+  getPlayheadPosition: () => 0,
+  getIsPlaying: () => false,
+};
+
+vi.mock('../core/KGCore', () => ({
+  KGCore: {
+    instance: () => mockCore,
+  },
+}));
+
+vi.mock('../core/config/ConfigManager', () => ({
+  ConfigManager: {
+    instance: () => ({
+      getIsInitialized: () => true,
+      get: () => false,
+    }),
+  },
+}));
+
+describe('projectStore piano roll state', () => {
+  beforeEach(() => {
+    vi.resetModules();
+  });
+
+  it('clears hybrid state when opening a MIDI region', async () => {
+    const { useProjectStore } = await import('./projectStore');
+
+    act(() => {
+      useProjectStore.getState().openHybridMode('midi-a', 'audio-a');
+    });
+
+    let state = useProjectStore.getState();
+    expect(state.pianoRollMode).toBe('hybrid');
+    expect(state.activeRegionId).toBe('midi-a');
+    expect(state.hybridAudioRegionId).toBe('audio-a');
+
+    act(() => {
+      useProjectStore.getState().openMidiPianoRoll('midi-b');
+    });
+
+    state = useProjectStore.getState();
+    expect(state.showPianoRoll).toBe(true);
+    expect(state.pianoRollMode).toBe('midi-edit');
+    expect(state.activeRegionId).toBe('midi-b');
+    expect(state.hybridAudioRegionId).toBeNull();
+  });
+});

src/stores/projectStore.ts

@@ -78,6 +78,8 @@ interface ProjectState {
   // Piano roll state
   showPianoRoll: boolean;
   activeRegionId: string | null;
+  pianoRollMode: 'midi-edit' | 'spectrogram' | 'hybrid';
+  hybridAudioRegionId: string | null;
   
   // ChatBox state
   showChatBox: boolean;
@@ -108,6 +110,12 @@ interface ProjectState {
   undoDescription: string | null;
   redoDescription: string | null;
 
+  // Cross-component scroll request state
+  requestMainContentScroll: (beatPosition: number) => void;
+  requestPianoRollScroll: (beatPosition: number) => void;
+  mainContentScrollRequest: number | null;
+  pianoRollScrollRequest: number | null;
+  
   // Actions
   setProjectName: (name: string) => void;
   setSavedProjectName: (name: string) => void;
@@ -146,6 +154,9 @@ interface ProjectState {
   // Piano roll actions
   setShowPianoRoll: (show: boolean) => void;
   setActiveRegionId: (regionId: string | null) => void;
+  openMidiPianoRoll: (regionId: string) => void;
+  openSpectrogramViewer: (regionId: string) => void;
+  openHybridMode: (midiRegionId: string, audioRegionId: string) => void;
   
   // Project state cleanup
   cleanupProjectState: () => void;
@@ -304,6 +315,8 @@ export const useProjectStore = create<ProjectState>((set, get) => {
     // Initial piano roll state
     showPianoRoll: false,
     activeRegionId: null,
+    pianoRollMode: 'midi-edit' as const,
+    hybridAudioRegionId: null,
     
     // Initial ChatBox state
     showChatBox: initialChatBoxState,
@@ -333,6 +346,10 @@ export const useProjectStore = create<ProjectState>((set, get) => {
     recordingNotes: [],
     recordingOriginalPlayhead: 0,
 
+    // Initial cross-component scroll request state
+    mainContentScrollRequest: null,
+    pianoRollScrollRequest: null,
+
     // Actions
     setProjectName: (name: string) => {
       try {
@@ -786,6 +803,14 @@ export const useProjectStore = create<ProjectState>((set, get) => {
       set({ autoScrollEnabled: enabled });
     },
 
+    requestMainContentScroll: (beatPosition: number) => {
+      set({ mainContentScrollRequest: beatPosition });
+    },
+
+    requestPianoRollScroll: (beatPosition: number) => {
+      set({ pianoRollScrollRequest: beatPosition });
+    },
+
     startPlaying: async () => {
       await KGCore.instance().startPlaying();
       set({ isPlaying: true, autoScrollEnabled: true });
@@ -1033,13 +1058,25 @@ export const useProjectStore = create<ProjectState>((set, get) => {
       set({ activeRegionId: regionId });
     },
 
+    openMidiPianoRoll: (regionId: string) => {
+      set({ showPianoRoll: true, activeRegionId: regionId, pianoRollMode: 'midi-edit', hybridAudioRegionId: null });
+    },
+
+    openSpectrogramViewer: (regionId: string) => {
+      set({ showPianoRoll: true, activeRegionId: regionId, pianoRollMode: 'spectrogram', hybridAudioRegionId: null });
+    },
+
+    openHybridMode: (midiRegionId: string, audioRegionId: string) => {
+      set({ showPianoRoll: true, activeRegionId: midiRegionId, hybridAudioRegionId: audioRegionId, pianoRollMode: 'hybrid' });
+    },
+    
     // Project state cleanup - used when starting new/loading projects
     cleanupProjectState: () => {
       // Close piano roll if it's visible
       set({ showPianoRoll: false });
 
-      // Clear active region
+      // Clear active region and hybrid state
-      set({ activeRegionId: null });
+      set({ activeRegionId: null, hybridAudioRegionId: null, pianoRollMode: 'midi-edit' });
       
       // Clear any selected items
       KGCore.instance().clearSelectedItems();

src/styles/variables.css

@@ -2,6 +2,7 @@
   --time-signature-numerator: 4;
   --max-number-of-bars: 32;
   --track-grid-bar-width: 40px;
+  --track-info-panel-width: 200px;
   --region-piano-key-width: 60px;
   --region-piano-key-height: 20px;
   --region-grid-beat-width: 40px;

src/workers/spectrogramWorker.ts

@@ -0,0 +1,103 @@
+import FFT from 'fft.js';
+
+type WorkerScopeLike = typeof globalThis & {
+  onmessage: ((event: MessageEvent<SpectrogramRequest>) => void) | null;
+  postMessage: (message: SpectrogramResult, transfer: Transferable[]) => void;
+};
+
+const workerScope = self as WorkerScopeLike;
+
+export interface SpectrogramRequest {
+  pcm: Float32Array;
+  sampleRate: number;
+  clipStartOffsetSeconds: number;
+  regionDurationSeconds: number;
+  bpm: number;
+}
+
+export interface SpectrogramResult {
+  data: Float32Array; // [timeSteps × 128] row-major, row = time step, col = pitch 0-127
+  timeSteps: number;
+}
+
+const FFT_SIZE = 8192;
+const HOP_SIZE = 1024;
+const PITCH_BINS = 128;
+
+function hannWindow(size: number): Float32Array {
+  const w = new Float32Array(size);
+  for (let i = 0; i < size; i++) {
+    w[i] = 0.5 * (1 - Math.cos((2 * Math.PI * i) / (size - 1)));
+  }
+  return w;
+}
+
+workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
+  const { pcm, sampleRate, clipStartOffsetSeconds, regionDurationSeconds } = e.data;
+
+  const startSample = Math.floor(clipStartOffsetSeconds * sampleRate);
+  const endSample = Math.min(pcm.length, startSample + Math.ceil(regionDurationSeconds * sampleRate));
+  const regionSamples = pcm.subarray(startSample, endSample);
+
+  const fft = new FFT(FFT_SIZE);
+  const hann = hannWindow(FFT_SIZE);
+  const complexOut = fft.createComplexArray() as number[];
+  const inputPadded = new Float32Array(FFT_SIZE);
+
+  const totalHops = Math.max(1, Math.ceil((regionSamples.length - FFT_SIZE) / HOP_SIZE) + 1);
+  const result = new Float32Array(totalHops * PITCH_BINS);
+
+  let maxVal = 0;
+
+  for (let hop = 0; hop < totalHops; hop++) {
+    const offset = hop * HOP_SIZE;
+
+    // Fill windowed frame (zero-pad at end if needed)
+    inputPadded.fill(0);
+    const available = Math.min(FFT_SIZE, regionSamples.length - offset);
+    for (let i = 0; i < available; i++) {
+      inputPadded[i] = regionSamples[offset + i] * hann[i];
+    }
+
+    fft.realTransform(complexOut, inputPadded as unknown as number[]);
+    fft.completeSpectrum(complexOut);
+
+    // Max-pool magnitude into pitch bins: keep the loudest FFT bin per semitone,
+    // rather than summing. Summing inflates every bin by how many FFT bins land there.
+    const pitchRow = hop * PITCH_BINS;
+    const numBins = FFT_SIZE / 2;
+
+    for (let bin = 1; bin < numBins; bin++) {
+      const freq = (bin * sampleRate) / FFT_SIZE;
+      if (freq < 20 || freq > 20000) continue;
+
+      // Convert frequency to MIDI pitch; clamp to piano roll range C0–B7 (MIDI 12–107)
+      const pitch = Math.round(69 + 12 * Math.log2(freq / 440));
+      if (pitch < 12 || pitch > 107) continue;
+
+      const re = complexOut[2 * bin];
+      const im = complexOut[2 * bin + 1];
+      const magnitude = Math.sqrt(re * re + im * im);
+
+      if (magnitude > result[pitchRow + pitch]) {
+        result[pitchRow + pitch] = magnitude;
+      }
+    }
+
+    // Track global max for normalization
+    for (let p = 0; p < PITCH_BINS; p++) {
+      if (result[pitchRow + p] > maxVal) maxVal = result[pitchRow + p];
+    }
+  }
+
+  // Linear normalization only — threshold and power curve are applied in the canvas
+  // renderer so changing them is instant (no need to re-run the FFT).
+  if (maxVal > 0) {
+    for (let i = 0; i < result.length; i++) {
+      result[i] = result[i] / maxVal;
+    }
+  }
+
+  const response: SpectrogramResult = { data: result, timeSteps: totalHops };
+  workerScope.postMessage(response, [result.buffer]);
+};