Merge pull request #31 from kilmc/add-extended-chord-support

[feat] Add support for extended chords
kilmc · Nov 6, 2023 · 357ce56 · 357ce56
2 parents f206287 + 001d49a
commit 357ce56
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diff --git a/.changeset/shaggy-birds-argue.md b/.changeset/shaggy-birds-argue.md
@@ -0,0 +1,5 @@
+---
+"@kilmc/music-fns": minor
+---
+
+Add support for 2nd, 4th, 5th, 6th, 9th, 11th and 13th chords
diff --git a/src/converters/chords/chordInfoToBaseIntervals.ts b/src/converters/chords/chordInfoToBaseIntervals.ts
@@ -20,18 +20,66 @@ const seventhMap: Record<string, IntervalShorthand[]> = {
   'half-diminished': ['m7'],
 };
 
+const ninthMap: Record<string, IntervalShorthand[]> = {
+  major: ['M7', 'M9'],
+  dominant: ['m7', 'M9'],
+  minor: ['m7', 'M9'],
+};
+
+const eleventhMap: Record<string, IntervalShorthand[]> = {
+  major: ['M7', 'M9', 'P11'],
+  dominant: ['m7', 'M9', 'P11'],
+  minor: ['m7', 'M9', 'P11'],
+};
+
+const thirteenthMap: Record<string, IntervalShorthand[]> = {
+  major: ['M7', 'M9', 'M13'],
+  dominant: ['m7', 'M9', 'P11', 'M13'],
+  minor: ['m7', 'M9', 'M13'],
+};
+
 export const chordInfoToBaseIntervals = (
   chordInfo: ChordInfo
 ): IntervalShorthand[] => {
   const { type, quality } = chordInfo;
 
+  // second handled in createAddNotes as they're aliases
+
+  if (type === 'fourth') return ['P4', 'm7', 'm10'];
+  if (type === 'fifth') return ['P5', 'P8'];
+
+  if (type === 'sixth') {
+    return [...qualityMap[quality === undefined ? 'dominant' : quality], 'M6'];
+  }
+
   if (type === 'seventh') {
     return [
       ...qualityMap[quality === undefined ? 'dominant' : quality],
       ...seventhMap[quality === undefined ? 'dominant' : quality],
     ];
   }
 
+  if (type === 'ninth') {
+    return [
+      ...qualityMap[quality === undefined ? 'dominant' : quality],
+      ...ninthMap[quality === undefined ? 'dominant' : quality],
+    ];
+  }
+
+  if (type === 'eleventh') {
+    return [
+      ...qualityMap[quality === undefined ? 'dominant' : quality],
+      ...eleventhMap[quality === undefined ? 'dominant' : quality],
+    ];
+  }
+
+  if (type === 'thirteenth') {
+    return [
+      ...qualityMap[quality === undefined ? 'dominant' : quality],
+      ...thirteenthMap[quality === undefined ? 'dominant' : quality],
+    ];
+  }
+
   if (quality === 'major') return qualityMap[quality];
   if (quality === 'minor') return qualityMap[quality];
   if (quality === 'diminished') return qualityMap[quality];

diff --git a/src/public/getChord/createAddNotes.ts b/src/public/getChord/createAddNotes.ts
@@ -3,6 +3,9 @@ import { ChordInfo } from '../../readers/chords/readChord.js';
 import { transposeNote } from '../transposeNote.js';
 
 export const createAddNotes = (chord: ChordInfo) => {
+  if (chord.type === 'second') {
+    return transposeNote(chord.chordRoot, 'M2');
+  }
   if (!chord.isAddChord) return undefined;
 
   const intervalSymbol = /(4|11)/.test(String(chord.addDegree)) ? 'P' : 'M';

diff --git a/src/public/getChord/getChord.test.ts b/src/public/getChord/getChord.test.ts
@@ -191,6 +191,30 @@ describe('chord', () => {
     });
   });
 
+  describe('non-seventh extended chords', () => {
+    const addChords = [
+      { chordName: 'C2', notes: ['C', 'D', 'E', 'G'] },
+      { chordName: 'C4', notes: ['C', 'F', 'Bb', 'Eb'] },
+      { chordName: 'C5', notes: ['C', 'G', 'C'] },
+      { chordName: 'C6', notes: ['C', 'E', 'G', 'A'] },
+      { chordName: 'Cm6', notes: ['C', 'Eb', 'G', 'A'] },
+      { chordName: 'C6/9', notes: ['C', 'E', 'G', 'A', 'D'] },
+      { chordName: 'C9', notes: ['C', 'E', 'G', 'Bb', 'D'] },
+      { chordName: 'Cm9', notes: ['C', 'Eb', 'G', 'Bb', 'D'] },
+      { chordName: 'Cmaj9', notes: ['C', 'E', 'G', 'B', 'D'] },
+      { chordName: 'C11', notes: ['C', 'E', 'G', 'Bb', 'D', 'F'] },
+      { chordName: 'Cm11', notes: ['C', 'Eb', 'G', 'Bb', 'D', 'F'] },
+      { chordName: 'C13', notes: ['C', 'E', 'G', 'Bb', 'D', 'F', 'A'] },
+      { chordName: 'Cm13', notes: ['C', 'Eb', 'G', 'Bb', 'D', 'A'] },
+      { chordName: 'Cmaj13', notes: ['C', 'E', 'G', 'B', 'D', 'A'] },
+    ];
+    it.each(addChords)('$chordName', ({ chordName, notes }) => {
+      expect(
+        getChord(chordName)?.notes?.map((note) => note?.name)
+      ).toStrictEqual(notes);
+    });
+  });
+
   describe('add chords', () => {
     const addChords = [
       { chordName: 'Cadd2', notes: ['C', 'D', 'E', 'G'] },

diff --git a/src/readers/chords/readAddInfo.ts b/src/readers/chords/readAddInfo.ts
@@ -6,6 +6,15 @@ export const readAddInfo = (
   const regex = /add(2|4|9|11|13)/;
   const match = input.match(regex)?.slice(1, 2).at(0);
 
+  const sixNineRegex = /6\/9/;
+
+  if (sixNineRegex.test(input)) {
+    return {
+      isAddChord: true,
+      addDegree: 9,
+    };
+  }
+
   if (match === undefined) {
     return {
       isAddChord: false,

diff --git a/src/readers/chords/readChord.test.ts b/src/readers/chords/readChord.test.ts
@@ -117,13 +117,26 @@ describe('readChord', () => {
       });
     });
 
+    it('six-nine chords', () => {
+      expect(readChord('B6/9')).toStrictEqual({
+        ...empty,
+        input: 'B6/9',
+        chordRoot: 'B',
+        rootNote: 'B',
+        quality: 'major',
+        type: 'sixth',
+        isAddChord: true,
+        addDegree: 9,
+      });
+    });
+
     it('ninth chords', () => {
       expect(readChord('C9')).toStrictEqual({
         ...empty,
         input: 'C9',
         chordRoot: 'C',
         rootNote: 'C',
-        quality: 'major',
+        quality: 'dominant',
         type: 'ninth',
       });
     });
@@ -134,7 +147,7 @@ describe('readChord', () => {
         input: 'C11',
         chordRoot: 'C',
         rootNote: 'C',
-        quality: 'major',
+        quality: 'dominant',
         type: 'eleventh',
       });
     });
@@ -145,7 +158,7 @@ describe('readChord', () => {
         input: 'C13',
         chordRoot: 'C',
         rootNote: 'C',
-        quality: 'major',
+        quality: 'dominant',
         type: 'thirteenth',
       });
     });

diff --git a/src/readers/chords/readChordQuality.ts b/src/readers/chords/readChordQuality.ts
@@ -17,12 +17,17 @@ export const readChordQuality = (
   const regex = new RegExp(`${noteRegex.source}(${chordQualityRegex.source})?`);
   const quality = input.match(regex)?.slice(3, 4)[0];
 
-  if (quality === undefined && type === 'seventh') return 'dominant';
+  const hasQuality = quality !== undefined;
+  const hasType = type !== undefined;
 
   if (
-    quality === undefined ||
-    majorChordIdentifiers.some((i) => quality === i)
-  ) {
+    !hasQuality &&
+    hasType &&
+    ['seventh', 'ninth', 'eleventh', 'thirteenth'].includes(type)
+  )
+    return 'dominant';
+
+  if (!hasQuality || majorChordIdentifiers.some((i) => quality === i)) {
     return 'major';
   }