feat: add functions to convert between types of note representations …

…- freqToMidi, pitchToMidi, etc
Melodic-Mind · Aug 19, 2023 · 4e257d7 · 4e257d7
1 parent bcdee5b
commit 4e257d7
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Showing 2 changed files with 60 additions and 6 deletions.
diff --git a/src/utilities/ScientificFunctions.ts b/src/utilities/ScientificFunctions.ts
@@ -17,6 +17,14 @@ export function freqFromPitch(note: Note): number {
   ) * PITCH_STANDARD.frequency;
 }
 
+export function freqToPitch(frequency: number): Note {
+  const midi = freqToMidi(frequency);
+  const pitchClass = midi % NUMBER_OF_PITCH_CLASSES;
+  const octave = Math.floor(midi / NUMBER_OF_PITCH_CLASSES) - 1;
+  const note = `${FLAT_CLASS_NOTES[pitchClass]}${octave}`;
+  return note as Note;
+}
+
 /**
  * Turns a midi value to frequency.
  * @param {Number} midi
@@ -62,3 +70,23 @@ export function centsOffFromFreq(frequency: number, midi: number): number {
 export function midiToFreq(realNumber: number): number {
   return PITCH_STANDARD.frequency * (Math.pow(2, (realNumber - PITCH_STANDARD.midi) / NUMBER_OF_PITCH_CLASSES));
 }
+
+/**
+ * Convert MIDI value to pitch.
+ * @param {Number} midi
+ * @returns {Note}
+ */
+export function midiToPitch(midi: number): Note {
+  const freq = freqFromMidi(midi);
+  return freqToPitch(freq);
+}
+
+/**
+ * Convert pitch to MIDI value.
+ * @param {Note} pitch
+ * @returns {number}
+ */
+export function pitchToMidi(note: Note): number {
+  const freq = freqFromPitch(note);
+  return freqToMidi(freq);
+}
diff --git a/test/utilities/scientific-functions.spec.js b/test/utilities/scientific-functions.spec.js
@@ -1,11 +1,13 @@
-import { freqFromPitch, freqToMidi, midiToFreq } from '../../lib/index.js';
+import { freqFromPitch, freqToMidi, midiToFreq, freqToPitch, midiToPitch, pitchToMidi } from '../../lib/index.js';
 
-describe('Scientific functions', () => {
+describe.only('Scientific functions', () => {
   it('#freqFromPitch', () => {
-    const note   = 'A4';
-    const pitch2 = 'E5';
-    expect(freqFromPitch(note)).to.eql(440);
-    expect(Math.ceil(freqFromPitch(pitch2))).to.eql(660);
+    expect(freqFromPitch('A4')).to.eql(440);
+    expect(Math.ceil(freqFromPitch('E5'))).to.eql(660);
+    expect(Math.ceil(freqFromPitch('F4'))).to.eql(350);
+    expect(Math.ceil(freqFromPitch('C4'))).to.eql(262);
+    expect(Math.ceil(freqFromPitch('Db4'))).to.eql(278);
+    expect(Math.ceil(freqFromPitch('C#4'))).to.eql(278);
   });
 
   it('#freqToMidi', () => {
@@ -17,4 +19,28 @@ describe('Scientific functions', () => {
     expect(midiToFreq(69)).to.eql(440);
     expect(midiToFreq(57)).to.eql(220);
   });
+  it('#freqToPitch', () => {
+    expect(freqToPitch(69.3)).to.eql('Db2');
+    expect(freqToPitch(440)).to.eql('A4');
+    expect(freqToPitch(220)).to.eql('A3');
+    expect(freqToPitch(660)).to.eql('E5');
+    expect(freqToPitch(349.23)).to.eql('F4');
+  });
+  it('#midiToPitch', () => {
+    expect(midiToPitch(69)).to.eql('A4');
+    expect(midiToPitch(57)).to.eql('A3');
+    expect(midiToPitch(64)).to.eql('E4');
+    expect(midiToPitch(53)).to.eql('F3');
+    expect(midiToPitch(60)).to.eql('C4');
+    expect(midiToPitch(61)).to.eql('Db4');
+  });
+  it('#pitchToMidi', () => {
+    expect(pitchToMidi('A4')).to.eql(69);
+    expect(pitchToMidi('A3')).to.eql(57);
+    expect(pitchToMidi('E4')).to.eql(64);
+    expect(pitchToMidi('F3')).to.eql(53);
+    expect(pitchToMidi('C4')).to.eql(60);
+    expect(pitchToMidi('Db4')).to.eql(61);
+    expect(pitchToMidi('C#4')).to.eql(61);
+  });
 });