feat: improve spectrogram pitch mapping and vertical smoothing

src/components/piano-roll/SpectrogramCanvas.tsx

@@ -5,6 +5,7 @@ import { KGAudioInterface } from '../../core/audio-interface/KGAudioInterface';
 import { KGAudioFileStorage } from '../../core/io/KGAudioFileStorage';
 import type { SpectrogramRequest, SpectrogramResult } from '../../workers/spectrogramWorker';
 import {
+  SPECTROGRAM_FULL_SEMITONES,
   getSpectrogramVisibleBinRange,
   normalizeSpectrogramHeightResolution,
   SPECTROGRAM_VISIBLE_SEMITONES,
@@ -52,6 +53,25 @@ function hotColormap(v: number): [number, number, number] {
   return COLORMAP_STOPS[COLORMAP_STOPS.length - 1][1];
 }
 
+function smoothSpectrogramVertically(
+  source: Float32Array,
+  timeSteps: number,
+  pitchBins: number,
+): Float32Array {
+  const smoothed = new Float32Array(source.length);
+
+  for (let col = 0; col < timeSteps; col++) {
+    for (let row = 0; row < pitchBins; row++) {
+      const center = source[col * pitchBins + row];
+      const above = row > 0 ? source[col * pitchBins + row - 1] : center;
+      const below = row < pitchBins - 1 ? source[col * pitchBins + row + 1] : center;
+      smoothed[col * pitchBins + row] = above * 0.2 + center * 0.6 + below * 0.2;
+    }
+  }
+
+  return smoothed;
+}
+
 const SpectrogramCanvas: React.FC<SpectrogramCanvasProps> = ({
   audioRegion,
   trackId,
@@ -102,18 +122,21 @@ const SpectrogramCanvas: React.FC<SpectrogramCanvasProps> = ({
 
     // Convert dB threshold to linear: values below this → black
     const linearThreshold = Math.pow(10, thresholdDb / 20);
-    const visibleRange = getSpectrogramVisibleBinRange(heightResolution);
+    const analysisResolution = result.pitchBins / SPECTROGRAM_FULL_SEMITONES;
+    const visibleRange = getSpectrogramVisibleBinRange(analysisResolution);
     const visiblePitchBins = visibleRange.end - visibleRange.start;
 
     // 1. Paint at natural spectrogram resolution onto an offscreen canvas.
     //    Result data is low-to-high pitch; draw only the visible C0-B7 window, reversed for display.
-    const offscreen = document.createElement('canvas');
-    offscreen.width = result.timeSteps;
-    offscreen.height = visiblePitchBins;
-    const offCtx = offscreen.getContext('2d');
-    if (!offCtx) return;
+    const smoothedData = smoothSpectrogramVertically(result.data, result.timeSteps, result.pitchBins);
 
-    const imgData = offCtx.createImageData(result.timeSteps, visiblePitchBins);
+    const sourceCanvas = document.createElement('canvas');
+    sourceCanvas.width = result.timeSteps;
+    sourceCanvas.height = visiblePitchBins;
+    const sourceCtx = sourceCanvas.getContext('2d');
+    if (!sourceCtx) return;
+
+    const imgData = sourceCtx.createImageData(result.timeSteps, visiblePitchBins);
     const pixels = imgData.data;
 
     for (let row = 0; row < visiblePitchBins; row++) {
@@ -122,7 +145,7 @@ const SpectrogramCanvas: React.FC<SpectrogramCanvasProps> = ({
         const idx = (row * result.timeSteps + col) * 4;
         pixels[idx + 3] = 255; // always opaque
 
-        const raw = result.data[col * result.pitchBins + sourceRow];
+        const raw = smoothedData[col * result.pitchBins + sourceRow];
 
         // Hard threshold: values below noise floor → 0 (black)
         // Re-scale surviving range to [0,1] then apply power curve
@@ -139,14 +162,24 @@ const SpectrogramCanvas: React.FC<SpectrogramCanvasProps> = ({
       }
     }
 
-    offCtx.putImageData(imgData, 0, 0);
+    sourceCtx.putImageData(imgData, 0, 0);
 
-    // 2. Stretch onto the full canvas — browser bilinear filter smooths between bins.
+    const verticallyScaledCanvas = document.createElement('canvas');
+    verticallyScaledCanvas.width = result.timeSteps;
+    verticallyScaledCanvas.height = canvasHeight;
+    const verticallyScaledCtx = verticallyScaledCanvas.getContext('2d');
+    if (!verticallyScaledCtx) return;
+
+    // Scale only along the pitch axis so note starts/stops stay crisp in time.
+    verticallyScaledCtx.imageSmoothingEnabled = true;
+    verticallyScaledCtx.imageSmoothingQuality = 'high';
+    verticallyScaledCtx.drawImage(sourceCanvas, 0, 0, result.timeSteps, canvasHeight);
+
+    // 2. Stretch onto the full canvas horizontally without temporal blur.
     canvas.width = canvasWidth;
     canvas.height = canvasHeight;
-    ctx.imageSmoothingEnabled = true;
-    ctx.imageSmoothingQuality = 'high';
-    ctx.drawImage(offscreen, 0, 0, canvasWidth, canvasHeight);
+    ctx.imageSmoothingEnabled = false;
+    ctx.drawImage(verticallyScaledCanvas, 0, 0, canvasWidth, canvasHeight);
 
     // Store natural width and apply current zoom as CSS stretch (no pixel recompute on zoom)
     naturalWidthRef.current = canvasWidth;

src/util/spectrogramUtil.test.ts

@@ -1,7 +1,10 @@
 import { describe, expect, it } from 'vitest';
 import {
+  frequencyToMidiPitch,
+  getSpectrogramAnalysisResolution,
   getSpectrogramPitchBinCount,
   getSpectrogramVisibleBinRange,
+  mapFrequencyToSpectrogramPosition,
   mapMidiPitchToSpectrogramPosition,
   normalizeSpectrogramHeightResolution,
 } from './spectrogramUtil';
@@ -21,6 +24,12 @@ describe('spectrogramUtil', () => {
     expect(getSpectrogramPitchBinCount(5)).toBe(640);
   });
 
+  it('doubles the internal analysis resolution for each user-facing option', () => {
+    expect(getSpectrogramAnalysisResolution(1)).toBe(2);
+    expect(getSpectrogramAnalysisResolution(3)).toBe(6);
+    expect(getSpectrogramAnalysisResolution(5)).toBe(10);
+  });
+
   it('maps MIDI pitches into full-range spectrogram positions', () => {
     expect(mapMidiPitchToSpectrogramPosition(0, 1)).toBe(0);
     expect(mapMidiPitchToSpectrogramPosition(12.5, 3)).toBe(38.5);
@@ -29,6 +38,12 @@ describe('spectrogramUtil', () => {
     expect(mapMidiPitchToSpectrogramPosition(128, 3)).toBeNull();
   });
 
+  it('converts frequencies into MIDI pitch space and spectrogram positions', () => {
+    expect(frequencyToMidiPitch(440)).toBeCloseTo(69, 6);
+    expect(mapFrequencyToSpectrogramPosition(440, 5)).toBeCloseTo(347, 6);
+    expect(frequencyToMidiPitch(0)).toBeNull();
+  });
+
   it('derives the visible C0-B7 subrange inside the full-resolution buffer', () => {
     expect(getSpectrogramVisibleBinRange(1)).toEqual({ start: 12, end: 108 });
     expect(getSpectrogramVisibleBinRange(3)).toEqual({ start: 36, end: 324 });

src/util/spectrogramUtil.ts

@@ -6,6 +6,7 @@ export const SPECTROGRAM_FULL_SEMITONES =
   SPECTROGRAM_FULL_MAX_MIDI_PITCH - SPECTROGRAM_FULL_MIN_MIDI_PITCH + 1;
 export const SPECTROGRAM_VISIBLE_SEMITONES =
   SPECTROGRAM_MAX_MIDI_PITCH - SPECTROGRAM_MIN_MIDI_PITCH + 1;
+export const SPECTROGRAM_ANALYSIS_RESOLUTION_MULTIPLIER = 2;
 
 export type SpectrogramHeightResolution = 1 | 3 | 5;
 
@@ -19,13 +20,13 @@ export function normalizeSpectrogramHeightResolution(value: unknown): Spectrogra
 }
 
 export function getSpectrogramPitchBinCount(
-  resolution: SpectrogramHeightResolution,
+  resolution: number,
 ): number {
   return SPECTROGRAM_FULL_SEMITONES * resolution;
 }
 
 export function getSpectrogramVisibleBinRange(
-  resolution: SpectrogramHeightResolution,
+  resolution: number,
 ): { start: number; end: number } {
   return {
     start: (SPECTROGRAM_MIN_MIDI_PITCH - SPECTROGRAM_FULL_MIN_MIDI_PITCH) * resolution,
@@ -33,9 +34,15 @@ export function getSpectrogramVisibleBinRange(
   };
 }
 
+export function getSpectrogramAnalysisResolution(
+  resolution: SpectrogramHeightResolution,
+): number {
+  return resolution * SPECTROGRAM_ANALYSIS_RESOLUTION_MULTIPLIER;
+}
+
 export function mapMidiPitchToSpectrogramPosition(
   midiPitch: number,
-  resolution: SpectrogramHeightResolution,
+  resolution: number,
 ): number | null {
   const pitchOffset = midiPitch - SPECTROGRAM_FULL_MIN_MIDI_PITCH;
   if (pitchOffset < 0 || pitchOffset > SPECTROGRAM_FULL_MAX_MIDI_PITCH) {
@@ -48,3 +55,21 @@ export function mapMidiPitchToSpectrogramPosition(
   const maxBin = getSpectrogramPitchBinCount(resolution) - 1;
   return Math.max(0, Math.min(maxBin, scaled));
 }
+
+export function frequencyToMidiPitch(frequency: number): number | null {
+  if (!Number.isFinite(frequency) || frequency <= 0) {
+    return null;
+  }
+  return 69 + 12 * Math.log2(frequency / 440);
+}
+
+export function mapFrequencyToSpectrogramPosition(
+  frequency: number,
+  resolution: number,
+): number | null {
+  const midiPitch = frequencyToMidiPitch(frequency);
+  if (midiPitch === null) {
+    return null;
+  }
+  return mapMidiPitchToSpectrogramPosition(midiPitch, resolution);
+}

src/workers/spectrogramWorker.test.ts

@@ -0,0 +1,107 @@
+import { describe, expect, it } from 'vitest';
+import { getSpectrogramPitchBinCount, mapFrequencyToSpectrogramPosition } from '../util/spectrogramUtil';
+import {
+  estimatePeakFrequency,
+  getFrequencyBandEdges,
+  paintMagnitudeAcrossPitchSpan,
+} from './spectrogramWorker';
+
+const FFT_SIZE = 16384;
+const SAMPLE_RATE = 44100;
+const HZ_PER_BIN = SAMPLE_RATE / FFT_SIZE;
+
+function paintSpanForFrequency(
+  centerFrequency: number,
+  resolution: 1 | 3 | 5,
+  pitchBins = getSpectrogramPitchBinCount(resolution),
+): Float32Array {
+  const row = new Float32Array(pitchBins);
+  const { lowerFrequency, upperFrequency } = getFrequencyBandEdges(centerFrequency, HZ_PER_BIN);
+  const startPosition = mapFrequencyToSpectrogramPosition(lowerFrequency, resolution);
+  const endPosition = mapFrequencyToSpectrogramPosition(upperFrequency, resolution);
+  const centerPosition = mapFrequencyToSpectrogramPosition(centerFrequency, resolution);
+
+  if (startPosition === null || endPosition === null || centerPosition === null) {
+    throw new Error('Expected mapped pitch positions for test frequency span');
+  }
+
+  paintMagnitudeAcrossPitchSpan(
+    row,
+    0,
+    pitchBins,
+    Math.min(startPosition, endPosition),
+    Math.max(startPosition, endPosition),
+    centerPosition,
+    1,
+  );
+  return row;
+}
+
+describe('spectrogramWorker helpers', () => {
+  it('keeps adjacent low-register FFT bins continuous at 5x resolution', () => {
+    const pitchBins = getSpectrogramPitchBinCount(5);
+    const row = new Float32Array(pitchBins);
+    const binsAroundA1 = [10, 11];
+
+    for (const bin of binsAroundA1) {
+      const centerFrequency = bin * HZ_PER_BIN;
+      const { lowerFrequency, upperFrequency } = getFrequencyBandEdges(centerFrequency, HZ_PER_BIN);
+      const startPosition = mapFrequencyToSpectrogramPosition(lowerFrequency, 5);
+      const endPosition = mapFrequencyToSpectrogramPosition(upperFrequency, 5);
+      const centerPosition = mapFrequencyToSpectrogramPosition(centerFrequency, 5);
+
+      expect(startPosition).not.toBeNull();
+      expect(endPosition).not.toBeNull();
+      expect(centerPosition).not.toBeNull();
+
+      paintMagnitudeAcrossPitchSpan(
+        row,
+        0,
+        pitchBins,
+        Math.min(startPosition!, endPosition!),
+        Math.max(startPosition!, endPosition!),
+        centerPosition!,
+        1,
+      );
+    }
+
+    const nonZeroBins = [...row.entries()].filter(([, value]) => value > 0).map(([index]) => index);
+    expect(nonZeroBins.length).toBeGreaterThan(0);
+
+    for (let index = nonZeroBins[0]; index <= nonZeroBins[nonZeroBins.length - 1]; index++) {
+      expect(row[index]).toBeGreaterThan(0);
+    }
+  });
+
+  it('uses sub-bin interpolation to move the ridge closer to the true peak frequency', () => {
+    const magnitudes = new Float32Array([0, 0.3, 1.0, 0.82, 0.1, 0]);
+    const rawCenterFrequency = 2 * HZ_PER_BIN;
+    const interpolatedFrequency = estimatePeakFrequency(2, HZ_PER_BIN, magnitudes);
+    const expectedFrequency = (2.35 * HZ_PER_BIN);
+
+    expect(Math.abs(interpolatedFrequency - expectedFrequency)).toBeLessThan(
+      Math.abs(rawCenterFrequency - expectedFrequency),
+    );
+  });
+
+  it('leaves non-peak bins at their raw FFT center while still painting a span', () => {
+    const magnitudes = new Float32Array([0, 0.2, 0.4, 1.0, 0.8, 0.7, 0.2, 0]);
+    const centerFrequency = estimatePeakFrequency(4, HZ_PER_BIN, magnitudes);
+    expect(centerFrequency).toBeCloseTo(4 * HZ_PER_BIN, 6);
+
+    const row = paintSpanForFrequency(centerFrequency, 3);
+    expect(row.some(value => value > 0)).toBe(true);
+  });
+
+  it('maps edge-band spans into the valid spectrogram range without spilling outside the buffer', () => {
+    const lowRow = paintSpanForFrequency(20.5, 5);
+    const lowNonZeroBins = [...lowRow.entries()].filter(([, value]) => value > 0).map(([index]) => index);
+    expect(lowNonZeroBins.length).toBeGreaterThan(0);
+    expect(lowNonZeroBins[0]).toBeGreaterThanOrEqual(0);
+
+    const highRow = paintSpanForFrequency(12530, 5);
+    const highNonZeroBins = [...highRow.entries()].filter(([, value]) => value > 0).map(([index]) => index);
+    expect(highNonZeroBins.length).toBeGreaterThan(0);
+    expect(highNonZeroBins[highNonZeroBins.length - 1]).toBeLessThan(highRow.length);
+  });
+});

src/workers/spectrogramWorker.ts

@@ -1,7 +1,8 @@
 import FFT from 'fft.js';
 import {
+  getSpectrogramAnalysisResolution,
   getSpectrogramPitchBinCount,
-  mapMidiPitchToSpectrogramPosition,
+  mapFrequencyToSpectrogramPosition,
   normalizeSpectrogramHeightResolution,
   type SpectrogramHeightResolution,
 } from '../util/spectrogramUtil';
@@ -11,7 +12,7 @@ type WorkerScopeLike = typeof globalThis & {
   postMessage: (message: SpectrogramResult, transfer: Transferable[]) => void;
 };
 
-const workerScope = self as WorkerScopeLike;
+const workerScope = typeof self === 'undefined' ? null : self as WorkerScopeLike;
 
 export interface SpectrogramRequest {
   pcm: Float32Array;
@@ -28,8 +29,10 @@ export interface SpectrogramResult {
   pitchBins: number;
 }
 
-const FFT_SIZE = 8192;
+const FFT_SIZE = 16384;
 const HOP_SIZE = 1024;
+const MIN_SPECTROGRAM_FREQUENCY = 20;
+const MAX_SPECTROGRAM_FREQUENCY = 20000;
 
 function hannWindow(size: number): Float32Array {
   const w = new Float32Array(size);
@@ -39,24 +42,98 @@ function hannWindow(size: number): Float32Array {
   return w;
 }
 
-function spreadMagnitudeAcrossPitchBins(
+export function getFrequencyBandEdges(
+  centerFrequency: number,
+  hzPerBin: number,
+): { lowerFrequency: number; upperFrequency: number } {
+  const halfBandwidth = hzPerBin / 2;
+  return {
+    lowerFrequency: Math.max(Number.EPSILON, centerFrequency - halfBandwidth),
+    upperFrequency: centerFrequency + halfBandwidth,
+  };
+}
+
+export function estimateParabolicPeakOffset(
+  leftMagnitude: number,
+  centerMagnitude: number,
+  rightMagnitude: number,
+): number {
+  const denominator = leftMagnitude - 2 * centerMagnitude + rightMagnitude;
+  if (!Number.isFinite(denominator) || Math.abs(denominator) < Number.EPSILON) {
+    return 0;
+  }
+
+  const offset = 0.5 * (leftMagnitude - rightMagnitude) / denominator;
+  return Math.max(-0.5, Math.min(0.5, offset));
+}
+
+export function estimatePeakFrequency(
+  bin: number,
+  hzPerBin: number,
+  magnitudes: Float32Array,
+): number {
+  const centerFrequency = bin * hzPerBin;
+  if (bin <= 1 || bin >= magnitudes.length - 1) {
+    return centerFrequency;
+  }
+
+  const leftMagnitude = magnitudes[bin - 1];
+  const centerMagnitude = magnitudes[bin];
+  const rightMagnitude = magnitudes[bin + 1];
+
+  if (centerMagnitude <= leftMagnitude || centerMagnitude <= rightMagnitude) {
+    return centerFrequency;
+  }
+
+  return (bin + estimateParabolicPeakOffset(leftMagnitude, centerMagnitude, rightMagnitude)) * hzPerBin;
+}
+
+function getPitchSpanBounds(
+  lowerFrequency: number,
+  upperFrequency: number,
+  centerFrequency: number,
+  analysisResolution: number,
+): { startPosition: number; endPosition: number; centerPosition: number } | null {
+  const startPosition = mapFrequencyToSpectrogramPosition(lowerFrequency, analysisResolution);
+  const endPosition = mapFrequencyToSpectrogramPosition(upperFrequency, analysisResolution);
+  const centerPosition = mapFrequencyToSpectrogramPosition(centerFrequency, analysisResolution);
+
+  if (startPosition === null || endPosition === null || centerPosition === null) {
+    return null;
+  }
+
+  return {
+    startPosition: Math.min(startPosition, endPosition),
+    endPosition: Math.max(startPosition, endPosition),
+    centerPosition,
+  };
+}
+
+export function paintMagnitudeAcrossPitchSpan(
   result: Float32Array,
   pitchRow: number,
   pitchBins: number,
-  pitchPosition: number,
+  startPosition: number,
+  endPosition: number,
+  centerPosition: number,
   magnitude: number,
-  heightResolution: SpectrogramHeightResolution,
 ): void {
-  const spreadRadius = Math.max(0, heightResolution - 1);
-  const centerBin = Math.round(pitchPosition);
-  const startBin = Math.max(0, centerBin - spreadRadius);
-  const endBin = Math.min(pitchBins - 1, centerBin + spreadRadius);
-  const spreadWidth = spreadRadius + 1;
+  const clampedStart = Math.max(0, Math.min(startPosition, pitchBins - 1));
+  const clampedEnd = Math.max(0, Math.min(endPosition, pitchBins - 1));
+  const startBin = Math.max(0, Math.floor(clampedStart));
+  const endBin = Math.min(pitchBins - 1, Math.ceil(clampedEnd));
+  const spanWidth = Math.max(clampedEnd - clampedStart, 1);
 
   for (let targetBin = startBin; targetBin <= endBin; targetBin++) {
-    const distance = Math.abs(targetBin - pitchPosition);
-    const weight = Math.max(0, 1 - distance / spreadWidth);
-    if (weight <= 0) continue;
+    const cellStart = targetBin - 0.5;
+    const cellEnd = targetBin + 0.5;
+    const overlap = Math.max(0, Math.min(clampedEnd, cellEnd) - Math.max(clampedStart, cellStart));
+    if (overlap <= 0) continue;
+
+    const overlapWeight = Math.min(1, overlap);
+    const centerDistance = Math.abs(targetBin - centerPosition);
+    const centerWeight = Math.max(0, 1 - centerDistance / (spanWidth + 1));
+    const weight = Math.max(overlapWeight * (0.6 + 0.4 * centerWeight), overlapWeight * 0.35);
 
     const weightedMagnitude = magnitude * weight;
     const resultIndex = pitchRow + targetBin;
@@ -66,7 +143,7 @@ function spreadMagnitudeAcrossPitchBins(
   }
 }
 
-workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
+function handleSpectrogramRequest(e: MessageEvent<SpectrogramRequest>, scope: WorkerScopeLike): void {
   const {
     pcm,
     sampleRate,
@@ -75,7 +152,8 @@ workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
     heightResolution,
   } = e.data;
   const normalizedResolution = normalizeSpectrogramHeightResolution(heightResolution);
-  const pitchBins = getSpectrogramPitchBinCount(normalizedResolution);
+  const analysisResolution = getSpectrogramAnalysisResolution(normalizedResolution);
+  const pitchBins = getSpectrogramPitchBinCount(analysisResolution);
 
   const startSample = Math.floor(clipStartOffsetSeconds * sampleRate);
   const endSample = Math.min(pcm.length, startSample + Math.ceil(regionDurationSeconds * sampleRate));
@@ -85,6 +163,7 @@ workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
   const hann = hannWindow(FFT_SIZE);
   const complexOut = fft.createComplexArray() as number[];
   const inputPadded = new Float32Array(FFT_SIZE);
+  const hzPerBin = sampleRate / FFT_SIZE;
 
   const totalHops = Math.max(1, Math.ceil((regionSamples.length - FFT_SIZE) / HOP_SIZE) + 1);
   const result = new Float32Array(totalHops * pitchBins);
@@ -108,25 +187,44 @@ workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
     // rather than summing. Summing inflates every bin by how many FFT bins land there.
     const pitchRow = hop * pitchBins;
     const numBins = FFT_SIZE / 2;
+    const magnitudes = new Float32Array(numBins);
 
     for (let bin = 1; bin < numBins; bin++) {
-      const freq = (bin * sampleRate) / FFT_SIZE;
-      if (freq < 20 || freq > 20000) continue;
-
-      const midiPitch = 69 + 12 * Math.log2(freq / 440);
-      const pitchPosition = mapMidiPitchToSpectrogramPosition(midiPitch, normalizedResolution);
-      if (pitchPosition === null) continue;
-
       const re = complexOut[2 * bin];
       const im = complexOut[2 * bin + 1];
-      const magnitude = Math.sqrt(re * re + im * im);
-      spreadMagnitudeAcrossPitchBins(
+      magnitudes[bin] = Math.sqrt(re * re + im * im);
+    }
+
+    for (let bin = 1; bin < numBins; bin++) {
+      const centerFrequency = estimatePeakFrequency(bin, hzPerBin, magnitudes);
+      const { lowerFrequency, upperFrequency } = getFrequencyBandEdges(centerFrequency, hzPerBin);
+      if (upperFrequency < MIN_SPECTROGRAM_FREQUENCY || lowerFrequency > MAX_SPECTROGRAM_FREQUENCY) continue;
+
+      const clampedLowerFrequency = Math.max(lowerFrequency, MIN_SPECTROGRAM_FREQUENCY);
+      const clampedUpperFrequency = Math.min(upperFrequency, MAX_SPECTROGRAM_FREQUENCY);
+      const clampedCenterFrequency = Math.min(
+        clampedUpperFrequency,
+        Math.max(clampedLowerFrequency, centerFrequency),
+      );
+      const pitchSpan = getPitchSpanBounds(
+        clampedLowerFrequency,
+        clampedUpperFrequency,
+        clampedCenterFrequency,
+        analysisResolution,
+      );
+      if (!pitchSpan) continue;
+
+      const magnitude = magnitudes[bin];
+      if (magnitude <= 0) continue;
+
+      paintMagnitudeAcrossPitchSpan(
         result,
         pitchRow,
         pitchBins,
-        pitchPosition,
+        pitchSpan.startPosition,
+        pitchSpan.endPosition,
+        pitchSpan.centerPosition,
         magnitude,
-        normalizedResolution,
       );
     }
 
@@ -145,5 +243,11 @@ workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
   }
 
   const response: SpectrogramResult = { data: result, timeSteps: totalHops, pitchBins };
-  workerScope.postMessage(response, [result.buffer]);
-};
+  scope.postMessage(response, [result.buffer]);
+}
+
+if (workerScope) {
+  workerScope.onmessage = (e: MessageEvent<SpectrogramRequest>) => {
+    handleSpectrogramRequest(e, workerScope);
+  };
+}