node-easymidi is a simple event-based MIDI messaging wrapper for node-midi.

Install with NPM:

npm install easymidi

The module can interface with existing MIDI inputs/outputs or create virtual inputs/outputs. Here's a simple example to listen for note on events from an existing MIDI input:

var easymidi = require('easymidi');
var input = new easymidi.Input('MIDI Input Name');
input.on('noteon', function (msg) {
  // do something with msg
});

Here's an example of sending a note on message to an existing MIDI output:

var easymidi = require('easymidi');
var output = new easymidi.Output('MIDI Output Name');
output.send('noteon', {
  note: 64,
  velocity: 127,
  channel: 3
});

The Input and Output objects are EventEmitters and you can use the EventEmitter functions such as once(), removeListener(), and removeAllListeners() as well.

Virtual devices can be created by passing a true argument to the Input or Output constructors:

var virtualInput = new easymidi.Input('Virtual input name', true);
var virtualOutput = new easymidi.Output('Virtual output name', true);

You can get an array of existing MIDI input or output names using the getInputs() and getOutputs functions:

var inputs = easymidi.getInputs();
var outputs = easymidi.getOutputs();

When you're finished with a MIDI device you can close() it:

var input = new easymidi.Input('My input', true);
input.close();

var output = new easymidi.Output('My output', true);
output.close();

The following table describes the MIDI message types that are supported and the parameters of each:

Receive a noteon message:

input.on('noteon', function (params) {
  // params = {note: ..., velocity: ..., channel: ...}
});

Send a control change message:

output.send('cc', {
  controller: 37,
  value: 80,
  channel: 0
})

Listen for midi clock messages:

input.on('clock', function () {
  // do something on every clock tick
});

Send a sysex message.
Throws an error if array does not start with 0xf0 (240) and end with 0xf7 (247).

output.send('sysex',[240, 126, 1, 6, 1, 247]);

See the example programs for more examples.