feat: support n for voicing scales

+ simplify voicing logic

packages/tonal/test/tonleiter.test.mjs

@@ -18,6 +18,7 @@ import {
   note2midi,
   midi2note,
   voiceBelow,
+  scaleStep,
 } from '../tonleiter.mjs';
 
 describe('tonleiter', () => {
@@ -102,6 +103,17 @@ describe('tonleiter', () => {
     expect(midi2note(61)).toBe('Db4');
     expect(midi2note(61, true)).toBe('C#4');
   });
+  test('scaleStep', () => {
+    expect(scaleStep([60, 63, 67], 0)).toBe(60);
+    expect(scaleStep([60, 63, 67], 1)).toBe(63);
+    expect(scaleStep([60, 63, 67], 2)).toBe(67);
+    expect(scaleStep([60, 63, 67], 3)).toBe(72);
+    expect(scaleStep([60, 63, 67], 4)).toBe(75);
+    expect(scaleStep([60, 63, 67], -1)).toBe(55);
+    expect(scaleStep([60, 63, 67], -2)).toBe(51);
+    expect(scaleStep([60, 63, 67], -3)).toBe(48);
+    expect(scaleStep([60, 63, 67], -4)).toBe(43);
+  });
   test('voiceBelow', () => {
     const voicingDictionary = {
       m7: [

packages/tonal/tonleiter.mjs

@@ -61,7 +61,14 @@ export const midi2note = (midi, sharp = false) => {
   return pc + oct;
 };
 
-export function voiceBelow(maxNote, chord, voicingDictionary, offset = 0) {
+export function scaleStep(notes, offset) {
+  notes = notes.map((note) => (typeof note === 'string' ? note2midi(note) : note));
+  const octOffset = Math.floor(offset / notes.length) * 12;
+  offset = _mod(offset, 12);
+  return notes[offset % notes.length] + octOffset;
+}
+
+export function voiceBelow(maxNote, chord, voicingDictionary, offset = 0, n) {
   const [root, symbol] = tokenizeChord(chord);
   const maxPc = note2pc(maxNote);
   const maxChroma = pc2chroma(maxPc);
@@ -81,15 +88,18 @@ export function voiceBelow(maxNote, chord, voicingDictionary, offset = 0) {
     return diff;
   });
 
-  const octDiff =
-    offset >= 0 ? Math.ceil(offset / voicings.length) * 12 : Math.floor(Math.abs(offset) / voicings.length) * -12;
-  bestIndex = _mod(bestIndex + offset, voicings.length);
-  const voicing = voicings[bestIndex];
+  const octDiff = Math.ceil(offset / voicings.length) * 12;
+  const indexWithOffset = _mod(bestIndex + offset, voicings.length);
+  const voicing = voicings[indexWithOffset];
   const maxMidi = note2midi(maxNote);
-  const topMidi = maxMidi - chromaDiffs[bestIndex] + octDiff;
+  const topMidi = maxMidi - chromaDiffs[indexWithOffset] + octDiff;
 
   const voicingMidi = voicing.map((v) => topMidi - voicing[voicing.length - 1] + v);
-  return voicingMidi.map((n) => midi2note(n));
+  const notes = voicingMidi.map((n) => midi2note(n));
+  if (n !== undefined) {
+    return [scaleStep(notes, n)];
+  }
+  return notes;
 }
 
 // https://github.com/tidalcycles/strudel/blob/14184993d0ee7d69c47df57ac864a1a0f99a893f/packages/tonal/tonleiter.mjs

packages/tonal/voicings.mjs

@@ -139,13 +139,13 @@ export const rootNotes = register('rootNotes', function (octave, pat) {
 export const voicing = register('voicing', function (dictionary, pat) {
   return pat
     .fmap((value) => {
-      let { voiceMax: max, voiceBelow: below, voiceOffset: offset, chord, ...rest } = value;
+      let { voiceMax: max, voiceBelow: below, voiceOffset: offset, chord, n, ...rest } = value;
       let top = max || below;
       top = top?.note || top || 'c5';
       if (typeof dictionary === 'string') {
         dictionary = voicingRegistry[dictionary]?.dictionary;
       }
-      let notes = voiceBelow(top, chord, dictionary, offset);
+      let notes = voiceBelow(top, chord, dictionary, offset, n);
       if (below) {
         notes = notes.filter((n) => note2midi(n) !== note2midi(top));
       }