Midi-notefreq-pmb NPM

midi-notefreq-pmb

Calculate frequency from MIDI note number and vice versa.

This lib comes with tests and instructive¹ source code. (¹ at least for future me, hopefully.)

Usage

var mnf = require('midi-notefreq-pmb');

function testNote(noteName, expectMidiNote, expectFreqHz) {
  var midiNote = mnf.sciUK2midiNote(noteName);
  equal(midiNote, expectMidiNote);
  equal(mnf.midiNote2sciUK(expectMidiNote), noteName);
  equal(mnf.midiNote2freqHz(midiNote), expectFreqHz);
  equal(mnf.freqHz2midiNote(expectFreqHz), expectMidiNote);
}
testNote('C-1',   0,      8.175798915643707);
testNote('C4',   60,    261.6255653005986);
testNote('A4',   69,    440.0);
testNote('A3',   57,    220.0);
testNote('A5',   81,    880.0);
testNote('G9',  127,  12543.853951415975);

equal(mnf.sciUK2midiNote(['C-1', 'C4', 'A4', 'A3', 'A5', 'G9']),
                         [   0,   60,   69,   57,   81,  127 ]);

function testFreq(noteName, offset, freqHz) {
  var expectMidiNote = mnf.sciUK2midiNote(noteName) + offset;
  equal(mnf.freqHz2midiNote(freqHz), expectMidiNote);
  floatAlmostEqual(mnf.midiNote2freqHz(expectMidiNote), freqHz);
}
testFreq('A3',  0,                  220.0);
testFreq('A4',  0,                  440.0);
testFreq('A4',  0.42748691676866,   451.0);
testFreq('F#9', 0.72430607743638, 12345.6789);