transpose: support alls combinations of numbers and strings for notes and intervals

packages/tonal/test/tonal.test.mjs

@@ -7,7 +7,7 @@ This program is free software: you can redistribute it and/or modify it under th
 // import { strict as assert } from 'assert';
 
 import '../tonal.mjs'; // need to import this to add prototypes
-import { pure, n, seq } from '@strudel/core';
+import { pure, n, seq, note } from '@strudel/core';
 import { describe, it, expect } from 'vitest';
 import { mini } from '../../mini/mini.mjs';
 
@@ -44,4 +44,36 @@ describe('tonal', () => {
         .firstCycleValues.map((h) => h.note),
     ).toEqual(['C3', 'D3', 'E3']);
   });
+  it('transposes note numbers with interval numbers', () => {
+    expect(
+      note(40, 40, 40)
+        .transpose(0, 1, 2)
+        .firstCycleValues.map((h) => h.note),
+    ).toEqual([40, 41, 42]);
+    expect(seq(40, 40, 40).transpose(0, 1, 2).firstCycleValues).toEqual([40, 41, 42]);
+  });
+  it('transposes note numbers with interval strings', () => {
+    expect(
+      note(40, 40, 40)
+        .transpose('1P', '2M', '3m')
+        .firstCycleValues.map((h) => h.note),
+    ).toEqual([40, 42, 43]);
+    expect(seq(40, 40, 40).transpose('1P', '2M', '3m').firstCycleValues).toEqual([40, 42, 43]);
+  });
+  it('transposes note strings with interval numbers', () => {
+    expect(
+      note('c', 'c', 'c')
+        .transpose(0, 1, 2)
+        .firstCycleValues.map((h) => h.note),
+    ).toEqual(['C', 'Db', 'D']);
+    expect(seq('c', 'c', 'c').transpose(0, 1, 2).firstCycleValues).toEqual(['C', 'Db', 'D']);
+  });
+  it('transposes note strings with interval strings', () => {
+    expect(
+      note('c', 'c', 'c')
+        .transpose('1P', '2M', '3m')
+        .firstCycleValues.map((h) => h.note),
+    ).toEqual(['C', 'D', 'Eb']);
+    expect(seq('c', 'c', 'c').transpose('1P', '2M', '3m').firstCycleValues).toEqual(['C', 'D', 'Eb']);
+  });
 });

packages/tonal/tonal.mjs

@@ -96,18 +96,37 @@ function scaleOffset(scale, offset, note) {
 
 export const transpose = register('transpose', function (intervalOrSemitones, pat) {
   return pat.withHap((hap) => {
-    const interval = !isNaN(Number(intervalOrSemitones))
+    const note = hap.value.note ?? hap.value;
-      ? Interval.fromSemitones(intervalOrSemitones /*  as number */)
+    if (typeof note === 'number') {
-      : String(intervalOrSemitones);
+      // note is a number, so just add the number semitones of the interval
-    if (typeof hap.value === 'number') {
+      let semitones;
-      const semitones = typeof interval === 'string' ? Interval.semitones(interval) || 0 : interval;
+      if (typeof intervalOrSemitones === 'number') {
-      return hap.withValue(() => hap.value + semitones);
+        semitones = intervalOrSemitones;
+      } else if (typeof intervalOrSemitones === 'string') {
+        semitones = Interval.semitones(intervalOrSemitones) || 0;
+      }
+      const targetNote = note + semitones;
+      if (typeof hap.value === 'object') {
+        return hap.withValue(() => ({ ...hap.value, note: targetNote }));
+      }
+      return hap.withValue(() => targetNote);
     }
-    if (typeof hap.value === 'object')
+    if (typeof note !== 'string' || !isNote(note)) {
-      return hap.withValue(() => ({ ...hap.value, note: Note.simplify(Note.transpose(hap.value.note, interval)) }));
+      logger(`[tonal] transpose: not a note "${note}"`, 'warning');
+      return hap;
+    }
+    // note is a string, so we might be able to preserve harmonics if interval is a string as well
+    const interval = !isNaN(Number(intervalOrSemitones))
+      ? Interval.fromSemitones(intervalOrSemitones)
+      : String(intervalOrSemitones);
     // TODO: move simplify to player to preserve enharmonics
     // tone.js doesn't understand multiple sharps flats e.g. F##3 has to be turned into G3
-    return hap.withValue(() => Note.simplify(Note.transpose(hap.value, interval)));
+    // TODO: check if this is still relevant..
+    const targetNote = Note.simplify(Note.transpose(note, interval));
+    if (typeof hap.value === 'object') {
+      return hap.withValue(() => ({ ...hap.value, note: targetNote }));
+    }
+    return hap.withValue(() => targetNote);
   });
 });