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JZZ: MIDI library for Node.js and web-browsers

nodejs firefox chrome opera safari msie edge windows macos linux raspberry pi ios android
npm npm jsDelivr build Coverage Try jzz on RunKit

JZZ.js allows sending, receiving and playing MIDI messages in Node.js and all major browsers in Linux, MacOS and Windows. Some features are available on iOS and Android devices.

JZZ.js enables Web MIDI API in Node.js and those browsers that don't support it, and provides additional functionality to make developer's life easier.

For the best user experience, it's highly RECOMMENDED (though not required) to install the latest version of Jazz-Plugin and browser extensions from Chrome Web Store or Mozilla Add-ons or Apple App Store.


  • MIDI In/Out
  • User-defined MIDI nodes
  • MIDI files
  • MPE
  • Additional modules


npm install jzz --save
or yarn add jzz
or get the full development version and minified scripts from Github

Note: in the (unlikely) case you get into trouble installing the midi-test module, that requires special system configuration, you can safely remove it from the devDependencies by running npm remove midi-test --save-dev.


Plain HTML
<script src="JZZ.js"></script>
CDN (jsdelivr)
<script src=""></script>       // the latest version, or
<script src=""></script> // any particular version
CDN (unpkg)
<script src=""></script>       // the latest version, or
<script src=""></script> // any particular version
var JZZ = require('jzz');
TypeScript / ES6
import * as JZZ from 'jzz';
require(['JZZ'], function(JZZ) {


(Node.js example)
var navigator = require('jzz');
navigator.requestMIDIAccess().then(onSuccess, onFail);
// ...
navigator.close(); // This will close MIDI inputs,
                   // otherwise Node.js will wait for MIDI input forever.
// In browsers the funcion is neither defined nor required.


MIDI Output/Input
JZZ().or('Cannot start MIDI engine!')
     .openMidiOut().or('Cannot open MIDI Out port!')
     .wait(500).send([0x90,60,127]) // note on
     .wait(500).send([0x80,60,0]);  // note off
JZZ().openMidiIn().or('Cannot open MIDI In port!')
     .and(function() { console.log('MIDI-In: ',; })
     .connect(function(msg) { console.log(msg.toString()); })
Connecting MIDI nodes
var input = JZZ().openMidiIn();
var output = JZZ().openMidiOut();
var delay = JZZ.Widget({ _receive: function(msg) { this.wait(500).emit(msg); }});
Helpers and shortcuts
// All calls below will do the same job:
port.send([0x90, 61, 127]).wait(500).send([0x80, 61, 0]);   // arrays
port.send(0x90, 61, 127).wait(500).send(0x80, 61, 0);       // comma-separated
port.send(0x90, 'C#5', 127).wait(500).send(0x80, 'Db5', 0); // note names
port.noteOn(0, 'C#5', 127).wait(500).noteOff(0, 'B##4');    // helper functions
port.note(0, 'C#5', 127, 500);                              // another shortcut'C#5').wait(500).noteOff('C#5');          // using channels'C#5', 127, 500);                           // using channels
Asynchronous calls
// in the environments that support async/await:
async function playNote() {
  var midi = await JZZ();
  var port = await midi.openMidiOut();
  await port.noteOn(0, 'C5', 127);
  await port.wait(500);
  await port.noteOff(0, 'C5');
  await port.close();
// or:
async function playAnotherNote() {
  var port = await JZZ().openMidiOut();
  await port.noteOn(0, 'C5', 127).wait(500).noteOff(0, 'C5').close();
Virtual MIDI ports
var logger = JZZ.Widget({ _receive: function(msg) { console.log(msg.toString()); }});
JZZ.addMidiOut('Console Logger', logger);

// now it can be used as a port:
var port = JZZ().openMidiOut('Console Logger');
// ...

// substitute the native MIDIAccess
// to make virtual ports visible to the Web MIDI API code:
navigator.requestMIDIAccess = JZZ.requestMIDIAccess;
Frequency / MIDI conversion
JZZ.MIDI.freq('A5'); // => 440
JZZ.MIDI.freq(69);   // => 440
JZZ.MIDI.freq(69.5); // => 452.8929841231365
// from frequency:
JZZ.MIDI.midi(440);  // => 69
JZZ.MIDI.midi(450);  // => 69.38905773230853
// or from name:
JZZ.MIDI.midi('A5'); // => 69

Additional modules

Testing your MIDI application

Check the Getting Started page and the API reference for more information...