midi-player

A MIDI player which sends MIDI messages to connected devices.

This module provides a player which sends MIDI messages to connected devices. It schedules the messages with a look ahead of about 500 milliseconds. It does not directly rely on the Web MIDI API but expects a MIDIOutput to be passed as constructor argument. But theoretically that could be anything which implements the same interface.

Features of this fork

This is a fork of the original midi-player module by Chris Guttandin. I decided to fork it instead of attempting to merge back the changes into the upstream because I am adding features outside the scope that Chris had envisioned for the module. Nothing prevents such a merge to happen in the future, given we find enough time to integrate the codebases. In the meantime, I do my best to keep this fork updated with the latest upstream changes, and to contribute to the core functionality that Chris maintains.

Here are the features added in this fork:

Add support for MIDIOutput.clear() for browsers that implement it
Add attributes IMidiPlayer.state and IMidiPlayer.position
Add methods IMidiPlayer.pause(), IMidiPlayer.resume(), IMidiPlayer.stop(), IMidiPlayer.seek(position)
Send MIDI Control Change (CC) message "All Sound Off" on player pause/stop

The version numbering used in this fork is <major>.<minor>.<patch>-<upstream-major>.<upstream-minor>.<upstream-patch>.

Usage

npm install git://github.com/infojunkie/midi-player.git#infojunkie

The only exported function is a factory method to create new player instances.

import { create } from 'midi-player';

// This is a JSON object which represents a MIDI file.
const json = {
    division: 480,
    format: 1,
    tracks: [
        { channel: 0, delta: 0, noteOn: { noteNumber: 36, velocity: 100 } },
        { channel: 0, delta: 240, noteOff: { noteNumber: 36, velocity: 64 } },
        { delta: 0, endOfTrack: true }
    ]
};

// This is a quick & dirty approach to grab the first known MIDI output.
const midiAccess = await navigator.requestMIDIAccess();
const midiOutput = Array.from(midiAccess.outputs)[0];

const midiPlayer = create({ json, midiOutput });

// All MIDI messages have been sent when the promise returned by play() resolves.
await midiPlayer.play();

By default only control change, note off, note on and program change events will be sent. But it's possible to provide a custom filter function. The following player will only send note off and note on events.

const midiPlayer = create({
    filterMidiMessage: (event) => 'noteOff' in event || 'noteOn' in event
    // ... other options as described above
});

If you want to play a binary MIDI file you can use the midi-json-parser package to transform it into a compatible JSON representation.