fix: support extended chord symbols in chord-to-MIDI import

src/util/chordRegionImportUtil.ts

@@ -1,4 +1,4 @@
-import { Chord, Note } from 'tonal';
+import { Note } from 'tonal';
 import { KGChordRegion } from '../core/region/KGChordRegion';
 import { getChordMidiPitches, parseChordSymbol } from './chordUtil';
 
@@ -59,11 +59,6 @@ export function convertChordSymbolToMidiPitches(symbol: string): number[] | null
     return null;
   }
 
-  const tonalChord = Chord.get(descriptor.symbol);
-  if (tonalChord.empty) {
-    return null;
-  }
-
   const rootMidi = getBaseRootMidi(descriptor.symbol);
   if (rootMidi === null) {
     return null;

src/util/chordUtil.test.ts

@@ -39,6 +39,18 @@ describe('chordUtil', () => {
     })).toBe('A#7');
   });
 
+  it('canonicalizes extended seventh-family chords using standard shorthand', () => {
+    expect(parseChordSymbol('Am9')?.symbol).toBe('Am9');
+    expect(parseChordSymbol('Dm11')?.symbol).toBe('Dm11');
+    expect(parseChordSymbol('G13')?.symbol).toBe('G13');
+    expect(parseChordSymbol('Bbmaj9')?.symbol).toBe('Bbmaj9');
+    expect(buildChordSymbol({
+      root: 'C',
+      quality: 'sus4',
+      extensions: ['9'],
+    })).toBe('Csus4add9');
+  });
+
   it('rejects unsupported symbols deterministically', () => {
     expect(parseChordSymbol('C/E')).toBeNull();
     expect(parseChordSymbol('not-a-chord')).toBeNull();
@@ -52,6 +64,10 @@ describe('chordUtil', () => {
 
   it('formats the preview using standard chord display conventions', () => {
     expect(formatChordSymbolForDisplay('Bm7b5')).toBe('Bm7(♭5)');
+    expect(formatChordSymbolForDisplay('Am9')).toBe('Am9');
+    expect(formatChordSymbolForDisplay('Dm11')).toBe('Dm11');
+    expect(formatChordSymbolForDisplay('G13')).toBe('G13');
+    expect(formatChordSymbolForDisplay('Bbmaj9')).toBe('B♭maj9');
     expect(formatChordSymbolForDisplay('Bbmaj7#11')).toBe('B♭maj7(♯11)');
     expect(formatChordSymbolForDisplay('G#dim7')).toBe('G♯dim7');
   });
@@ -71,6 +87,13 @@ describe('chordUtil', () => {
     expect(convertChordSymbolToMidiPitches('Bm7b5')).toEqual([47, 59, 62, 65, 69]);
   });
 
+  it('maps extended chords into MIDI pitches without relying on tonal round-tripping', () => {
+    expect(convertChordSymbolToMidiPitches('Am9')).toEqual([45, 57, 60, 64, 67, 71]);
+    expect(convertChordSymbolToMidiPitches('Dm9')).toEqual([50, 62, 65, 69, 72, 76]);
+    expect(convertChordSymbolToMidiPitches('G13')).toEqual([43, 55, 59, 62, 65, 69, 76]);
+    expect(convertChordSymbolToMidiPitches('Bbmaj9')).toEqual([46, 58, 62, 65, 69, 72]);
+  });
+
   it('builds a multi-region import plan using timeline-relative note placement', () => {
     const chordA = new KGChordRegion('chord-1', 'global-chord', 3, 'C', 8, 4);
     const chordB = new KGChordRegion('chord-2', 'global-chord', 3, 'F', 12, 2);
@@ -133,6 +156,49 @@ describe('chordUtil', () => {
     ]);
   });
 
+  it('builds an import plan for extended chord progressions', () => {
+    const chordA = new KGChordRegion('chord-1', 'global-chord', 3, 'Am9', 0, 4);
+    const chordB = new KGChordRegion('chord-2', 'global-chord', 3, 'Dm9', 4, 4);
+    const chordC = new KGChordRegion('chord-3', 'global-chord', 3, 'G13', 8, 4);
+    const chordD = new KGChordRegion('chord-4', 'global-chord', 3, 'Bbmaj9', 12, 4);
+    const result = buildChordRegionImportPlan([chordD, chordB, chordA, chordC]);
+
+    expect(result.ok).toBe(true);
+    if (!result.ok) {
+      return;
+    }
+
+    expect(result.plan.sourceRegionIds).toEqual(['chord-1', 'chord-2', 'chord-3', 'chord-4']);
+    expect(result.plan.lengthInBeats).toBe(16);
+    expect(result.plan.notes).toEqual([
+      { startBeat: 0, endBeat: 4, pitch: 45, velocity: 127 },
+      { startBeat: 0, endBeat: 4, pitch: 57, velocity: 127 },
+      { startBeat: 0, endBeat: 4, pitch: 60, velocity: 127 },
+      { startBeat: 0, endBeat: 4, pitch: 64, velocity: 127 },
+      { startBeat: 0, endBeat: 4, pitch: 67, velocity: 127 },
+      { startBeat: 0, endBeat: 4, pitch: 71, velocity: 127 },
+      { startBeat: 4, endBeat: 8, pitch: 50, velocity: 127 },
+      { startBeat: 4, endBeat: 8, pitch: 62, velocity: 127 },
+      { startBeat: 4, endBeat: 8, pitch: 65, velocity: 127 },
+      { startBeat: 4, endBeat: 8, pitch: 69, velocity: 127 },
+      { startBeat: 4, endBeat: 8, pitch: 72, velocity: 127 },
+      { startBeat: 4, endBeat: 8, pitch: 76, velocity: 127 },
+      { startBeat: 8, endBeat: 12, pitch: 43, velocity: 127 },
+      { startBeat: 8, endBeat: 12, pitch: 55, velocity: 127 },
+      { startBeat: 8, endBeat: 12, pitch: 59, velocity: 127 },
+      { startBeat: 8, endBeat: 12, pitch: 62, velocity: 127 },
+      { startBeat: 8, endBeat: 12, pitch: 65, velocity: 127 },
+      { startBeat: 8, endBeat: 12, pitch: 69, velocity: 127 },
+      { startBeat: 8, endBeat: 12, pitch: 76, velocity: 127 },
+      { startBeat: 12, endBeat: 16, pitch: 46, velocity: 127 },
+      { startBeat: 12, endBeat: 16, pitch: 58, velocity: 127 },
+      { startBeat: 12, endBeat: 16, pitch: 62, velocity: 127 },
+      { startBeat: 12, endBeat: 16, pitch: 65, velocity: 127 },
+      { startBeat: 12, endBeat: 16, pitch: 69, velocity: 127 },
+      { startBeat: 12, endBeat: 16, pitch: 72, velocity: 127 },
+    ]);
+  });
+
   it('returns structured failure metadata for unsupported symbols', () => {
     const badChord = new KGChordRegion('chord-1', 'global-chord', 3, 'not-a-chord', 0, 4);
     const result = buildChordRegionImportPlan([badChord]);

src/util/chordUtil.ts

@@ -77,6 +77,57 @@ function hasExtension(descriptor: Pick<ChordDescriptor, 'extensions'>, extension
   return descriptor.extensions.includes(extension);
 }
 
+interface CollapsedNaturalExtension {
+  suffix: string;
+  consumed: ChordExtension[];
+}
+
+function getCollapsedNaturalExtension(
+  quality: ChordQuality,
+  extensions: ChordExtension[],
+): CollapsedNaturalExtension | null {
+  const has = (extension: ChordExtension) => extensions.includes(extension);
+  const consume = (...consumed: ChordExtension[]): ChordExtension[] => consumed.filter(has);
+
+  if (quality === 'maj' && has('maj7')) {
+    if (has('13')) {
+      return { suffix: 'maj13', consumed: consume('maj7', '9', '11', '13') };
+    }
+    if (has('11')) {
+      return { suffix: 'maj11', consumed: consume('maj7', '9', '11') };
+    }
+    if (has('9')) {
+      return { suffix: 'maj9', consumed: consume('maj7', '9') };
+    }
+  }
+
+  if (quality === 'maj' && has('7')) {
+    if (has('13')) {
+      return { suffix: '13', consumed: consume('7', '9', '11', '13') };
+    }
+    if (has('11')) {
+      return { suffix: '11', consumed: consume('7', '9', '11') };
+    }
+    if (has('9')) {
+      return { suffix: '9', consumed: consume('7', '9') };
+    }
+  }
+
+  if (quality === 'min' && has('7')) {
+    if (has('13')) {
+      return { suffix: 'm13', consumed: consume('7', '9', '11', '13') };
+    }
+    if (has('11')) {
+      return { suffix: 'm11', consumed: consume('7', '9', '11') };
+    }
+    if (has('9')) {
+      return { suffix: 'm9', consumed: consume('7', '9') };
+    }
+  }
+
+  return null;
+}
+
 function getDescriptorIntervals(descriptor: Pick<ChordDescriptor, 'quality' | 'extensions'>): string[] {
   const intervals = ['1P'];
 
@@ -416,6 +467,11 @@ export function buildChordSymbol(descriptor: Pick<ChordDescriptor, 'root' | 'qua
     symbol += 'maj7#5';
     remainingExtensions.delete('maj7');
     remainingExtensions.delete('#5');
+  } else {
+    const collapsedNaturalExtension = getCollapsedNaturalExtension(descriptor.quality, extensions);
+    if (collapsedNaturalExtension) {
+      symbol += collapsedNaturalExtension.suffix;
+      collapsedNaturalExtension.consumed.forEach(extension => remainingExtensions.delete(extension));
     } else {
       switch (descriptor.quality) {
         case 'maj':
@@ -456,6 +512,7 @@ export function buildChordSymbol(descriptor: Pick<ChordDescriptor, 'root' | 'qua
         remainingExtensions.delete('6');
       }
     }
+  }
 
   for (const extension of REMAINING_EXTENSION_ORDER) {
     if (!remainingExtensions.has(extension)) {
@@ -530,7 +587,13 @@ export function formatChordSymbolForDisplay(symbol: string): string {
   if (quality === 'dim' && extensions.includes('dim7')) {
     return `${accidentalDisplay(root)}dim7`;
   }
+  const collapsedNaturalExtension = getCollapsedNaturalExtension(quality, extensions);
+  const consumedCollapsedExtensions = new Set(collapsedNaturalExtension?.consumed ?? []);
   const baseQuality = (() => {
+    if (collapsedNaturalExtension) {
+      return '';
+    }
+
     switch (quality) {
       case 'maj':
         return '';
@@ -553,6 +616,10 @@ export function formatChordSymbolForDisplay(symbol: string): string {
   const parentheticalExtensions: string[] = [];
 
   for (const extension of extensions) {
+    if (consumedCollapsedExtensions.has(extension)) {
+      continue;
+    }
+
     if (quality === 'dim' && extension === 'b5' && !extensions.includes('7')) {
       continue;
     }
@@ -565,7 +632,9 @@ export function formatChordSymbolForDisplay(symbol: string): string {
     parentheticalExtensions.push(accidentalDisplay(extension));
   }
 
-  const inlineText = inlineExtensions.join('');
+  const inlineText = collapsedNaturalExtension
+    ? collapsedNaturalExtension.suffix
+    : inlineExtensions.join('');
   const parentheticalText = parentheticalExtensions.length > 0
     ? `(${parentheticalExtensions.join(', ')})`
     : '';