deno-midi

A Deno wrapper for the RtMidi C++ library that provides realtime MIDI I/O.

It uses pre-built binaries of the 6.0.0 version of the library for Windows, Linux and MacOS (x64 and arm64), so no need to install any dependencies. They’re built from my fork of the RtMidi library that adds some extra features.

It uses Deno FFI to call the C++ library. The bindings have been generated thanks to the great help from Aapo Alasuutari and his libclang_deno bindings generator. He’s also the author of the denonomicon which is a great resource for FFI.

Usage

Midi Input

import { MidiInput } from "https://deno.land/x/deno_midi/mod.ts";

const midi_in = new MidiInput();
// List the available ports.
console.log(midi_in.getPorts());
midi_in.openPort(0); // Open the first available port.
// Set a callback to receive the messages. It keeps the program alive.
midi_in.onMessage((deltaTime, message) => {
  console.log(`Message received at ${deltaTime} : ${message}`);
});
// Stop the callback when you're done.
midi_in.offMessage();
// Close the port.
midi_in.closePort();
// It's still possible to open an other port, otherwise you can free the device.
midi_in.freeDevice();

Midi Output

The API is very similar, except you can send MIDI messages.

import { MidiOutput } from "https://deno.land/x/deno_midi/mod.ts";

const midi_out = new MidiOutput();
console.log(midi_out.getPorts());

midi_out.openPort(0);

// Send a note on.
midi_out.sendMessage([0x90, 0x3C, 0x7F]);
// Send a note off after 1 second.
setTimeout(() => {
  midi_out.sendMessage([0x80, 0x3C, 0x2F]);
}, 1000);

A complete example can be found in the example folder.