Unlocking Musical Creativity with the Web MIDI API in JavaScript

The Web MIDI API in JavaScript is a powerful tool that enables web developers to interact with musical instruments directly from the browser. This guide will introduce the basics of the Web MIDI API, demonstrate how to access and manipulate MIDI devices, and provide practical examples to integrate music into web applications.

Introduction to Web MIDI API

The Web MIDI API facilitates communication between web applications and MIDI-enabled devices like keyboards and drum machines, allowing for the creation of interactive musical experiences.

Key Features of the Web MIDI API:

  • Device Connectivity: Connects directly to MIDI instruments from the web browser.
  • Real-Time Interaction: Enables dynamic music creation and manipulation in real-time.

Using the Web MIDI API

Accessing MIDI Devices

// Requesting access to MIDI devices
navigator.requestMIDIAccess().then((midiAccess) => {
  console.log('MIDI access obtained', midiAccess);
}, (err) => {
  console.error('Could not access MIDI devices', err);
// This code snippet initiates a request for MIDI devices connected to the user's computer.

Handling MIDI Input

// Handling incoming MIDI messages
function onMIDIMessage(message) {
  let [command, note, velocity] = message.data;
  console.log(`MIDI message received: Command=${command}, Note=${note}, Velocity=${velocity}`);
// This function logs each MIDI message received, detailing the command, note, and velocity.

Sending MIDI Output

// Sending a note through MIDI
function sendNoteOn(midiOutput, note, velocity) {
  midiOutput.send([0x90, note, velocity]); // Note on
  setTimeout(() => {
    midiOutput.send([0x80, note, 0x00]); // Note off
  }, 500);
// This function sends a 'note on' message and turns it off after 500 milliseconds.


The Web MIDI API opens up a realm of possibilities for web developers interested in music technology. By leveraging this API, developers can create engaging, interactive web applications that interact with musical instruments, enhancing the user's musical experience.

Practice Your Knowledge

What are the capabilities of the JavaScript Web MIDI API?

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