feat: implemented chord detection feature for MIDI regions

2026-05-25 23:22:42 -07:00
parent 275cfece99
commit 0f1bad4394
9 changed files with 1274 additions and 74 deletions
@@ -0,0 +1,117 @@
+import { describe, expect, it } from 'vitest';
+import { KGProject } from '../core/KGProject';
+import { KGMidiNote } from '../core/midi/KGMidiNote';
+import { KGMidiRegion } from '../core/region/KGMidiRegion';
+import {
+  DEFAULT_MIDI_CHORD_DETECTION_OPTIONS,
+  buildMidiChordWindowsForRegion,
+  detectChordsFromMidi,
+  type MidiChordDetectionOptions,
+} from './midiChordDetection';
+
+function createProject(): KGProject {
+  return new KGProject('Chord Test', 32, 0, 125, { numerator: 4, denominator: 4 });
+}
+
+function createRegion(notes: Array<{ startBeat: number; endBeat: number; pitch: number; velocity?: number }>, startFromBeat = 0, length = 4): KGMidiRegion {
+  const region = new KGMidiRegion('region-1', '1', 0, 'Region', startFromBeat, length);
+  notes.forEach((note, index) => {
+    region.addNote(new KGMidiNote(
+      `note-${index}`,
+      note.startBeat,
+      note.endBeat,
+      note.pitch,
+      note.velocity ?? 100,
+    ));
+  });
+  return region;
+}
+
+function detectRegionChords(
+  region: KGMidiRegion,
+  options?: Partial<MidiChordDetectionOptions>,
+) {
+  const project = createProject();
+  const windows = buildMidiChordWindowsForRegion(project, region);
+  return detectChordsFromMidi({
+    project,
+    region,
+    windows,
+    options: {
+      ...DEFAULT_MIDI_CHORD_DETECTION_OPTIONS,
+      ...options,
+    },
+  });
+}
+
+describe('midi chord detection', () => {
+  it('detects a clean minor triad', () => {
+    const region = createRegion([
+      { startBeat: 0, endBeat: 4, pitch: 45 },
+      { startBeat: 0, endBeat: 4, pitch: 57 },
+      { startBeat: 0, endBeat: 4, pitch: 60 },
+      { startBeat: 0, endBeat: 4, pitch: 64 },
+    ]);
+
+    expect(detectRegionChords(region)[0]?.symbol).toBe('Am');
+  });
+
+  it('detects a dominant seventh when enabled', () => {
+    const region = createRegion([
+      { startBeat: 0, endBeat: 4, pitch: 52 },
+      { startBeat: 0, endBeat: 4, pitch: 64 },
+      { startBeat: 0, endBeat: 4, pitch: 68 },
+      { startBeat: 0, endBeat: 4, pitch: 71 },
+      { startBeat: 0, endBeat: 4, pitch: 74 },
+    ]);
+
+    expect(detectRegionChords(region, { enableSevenths: true })[0]?.symbol).toBe('E7');
+  });
+
+  it('keeps short melody notes from flipping the chord', () => {
+    const region = createRegion([
+      { startBeat: 0, endBeat: 4, pitch: 45 },
+      { startBeat: 0, endBeat: 4, pitch: 57 },
+      { startBeat: 0, endBeat: 4, pitch: 60 },
+      { startBeat: 0, endBeat: 4, pitch: 64 },
+      { startBeat: 0.25, endBeat: 0.5, pitch: 67 },
+      { startBeat: 1.25, endBeat: 1.5, pitch: 71 },
+      { startBeat: 2.25, endBeat: 2.5, pitch: 74 },
+    ]);
+
+    expect(detectRegionChords(region)[0]?.symbol).toBe('Am');
+  });
+
+  it('prefers the sustained harmony over non-chord embellishments', () => {
+    const region = createRegion([
+      { startBeat: 0, endBeat: 4, pitch: 41 },
+      { startBeat: 0, endBeat: 4, pitch: 53 },
+      { startBeat: 0, endBeat: 4, pitch: 57 },
+      { startBeat: 0, endBeat: 4, pitch: 60 },
+      { startBeat: 0, endBeat: 0.25, pitch: 62 },
+      { startBeat: 1, endBeat: 1.25, pitch: 64 },
+      { startBeat: 2, endBeat: 2.25, pitch: 67 },
+    ]);
+
+    expect(detectRegionChords(region)[0]?.symbol).toBe('F');
+  });
+
+  it('returns no chord for sparse windows', () => {
+    const region = createRegion([
+      { startBeat: 0, endBeat: 0.5, pitch: 60 },
+    ]);
+
+    expect(detectRegionChords(region)[0]?.symbol).toBe('N');
+  });
+
+  it('resolves inversions to the intended root chord', () => {
+    const region = createRegion([
+      { startBeat: 0, endBeat: 4, pitch: 64 },
+      { startBeat: 0, endBeat: 4, pitch: 69 },
+      { startBeat: 0, endBeat: 4, pitch: 72 },
+      { startBeat: 0, endBeat: 4, pitch: 76 },
+    ]);
+
+    expect(detectRegionChords(region)[0]?.symbol).toBe('Am');
+  });
+});