Play MIDI files in the browser w/ Web Audio, WebAssembly, and libtimidity
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Play MIDI files in the browser w/ Web Audio, WebAssembly, and libtimidity

Play MIDI files in a browser with a simple API.

NO OPEN SOURCE LICENSE YET. If you want to use this, send me an email. I'm still figuring out what license to use.


This package is used on, the wayback machine for old-school MIDI files! Check out some examples here:


npm install timidity


  • Lightweight – Just 34 KB of JavaScript and 23 KB of lazy-loaded WebAssembly.
  • Simple – No bells and whistles. Just what is needed to play MIDI files.
  • Works with the FreePats General MIDI soundset.


const Timidity = require('timidity')

const player = new Timidity()

player.on('playing', () => {
  console.log(player.duration) // => 351.521


player = new Timidity([baseUrl])

Create a new MIDI player.

Optionally, provide a baseUrl to customize where the player will look for the lazy-loaded WebAssembly file libtimidity.wasm and the FreePats General MIDI soundset files. The default baseUrl is /.

For example, here is how to mount the necessary files at / with the express server:

const timidityPath = path.dirname(require.resolve('timidity'))
app.use('/', express.static(timidityPath))

const freepatsPath = path.dirname(require.resolve('freepats'))
app.use('/', express.static(freepatsPath))


This function loads the specified MIDI file urlOrBuf, which is a string path to the MIDI file or a Uint8Array which contains the MIDI file data.

This should be the first function called on a new Timidity instance.

Plays the currently loaded MIDI file.


Pauses the currently loaded MIDI file.

Seeks to a specified time in the MIDI file.

If the player is paused when the function is called, it will remain paused. If the function is called from another state (playing, etc.), the player will continue playing.


Returns the duration in seconds (number) of the currently playing MIDI file. Note that duration will return 0 until the file is loaded, which normally happens just before the playing event.


Returns the elapsed time in seconds since the MIDI file started playing.


Destroys the entire player instance, stops the current MIDI file from playing, cleans up all resources.

Note: It's best to reuse the same player instance for as long as possible. It is not recommended to call player.destroy() to stop or change MIDI files. Rather, just call player.pause() to pause or player.load() to load a new MIDI file.


Returns true if destroy() has been called on the player. Returns false otherwise.

player.on('error', (err) => {})

This event fires if a fatal error occurs in the player, including if a MIDI file is unable to be played.

player.on('timeupdate', (seconds) => {})

This event fires when the time indicated by the currentTime property has been updated.

player.on('unstarted', () => {})

This event fires when a new MIDI file is being loaded.

player.on('ended', () => {})

This event fires when a MIDI file has played until the end.

player.on('playing', () => {})

This event fires when a MIDI file starts playing.

player.on('paused', () => {})

This event fires when a MIDI file is paused.

player.on('buffering', () => {})

This event fires when a MIDI file is loading.


Copyright (c) Feross Aboukhadijeh.