MIDI Out

In addition to receiving MIDI events we can also send out MIDI events to trigger and control external hardware synths, keyboards and other devices. Sonic Pi provides a full set of fns for sending various MIDI messages such as:

Note on - midi_note_on
Note off - midi_note_off
Control change - midi_cc
Pitch bend - midi_pitch_bend
Clock ticks - midi_clock_tick

There are many other supported MIDI messages too - check out the API documentation for all the other fns that start with midi_.

Connecting to a MIDI Device

In order to send a MIDI message to an external device, we must first have connected it. Check out the subsection ‘Connecting a MIDI Controller’ in section 11.1 for further details. Note that if you’re using USB, connecting to a device which you’re sending to (rather than receiving from) is the same procedure. However, if you’re using the classic DIN connectors, make sure you connect to the MIDI out port of your computer. You should see your MIDI device listed in the preferences pane.

Sending MIDI events

The many midi_* fns work just like play, sample and synth in that they send a message at the current (logical) time. For example, to spread out calls to the midi_* fns you need to use sleep just like you did with play. Let’s take a look:

midi_note_on :e3, 50

This will send a MIDI note on event to the connected MIDI device with velocity 50. (Note that Sonic Pi will automatically convert notes in the form :e3 to their corresponding MIDI number such as 52 in this case.)

If your connected MIDI device is a synthesiser, you should be able to hear it playing a note. To disable it use midi_note_off:

midi_note_off :e3

Selecting a MIDI device

By default, Sonic Pi will send each MIDI message to all connected devices on all MIDI channels. This is to make it easy to work with a single connected device without having to configure anything. However, sometimes a MIDI device will treat MIDI channels in a special way (perhaps each note has a separate channel) and also you may wish to connect more than one MIDI device at the same time. In more complicated setups, you may wish to be more selective about which MIDI device receives which message(s) and on which channel.

We can specify which device to send to using the port: opt, using the device name as displayed in the preferences:

midi_note_on :e3, port: "moog_minitaur"

We can also specify which channel to send to using the channel: opt (using a value in the range 1-16):

midi_note_on :e3, channel: 3

Of course we can also specify both at the same time to send to a specific device on a specific channel:

midi_note_on :e3, port: "moog_minitaur", channel: 5

MIDI Studio

Finally, a really fun thing to do is to connect the audio output of your MIDI synthesiser to one of the audio inputs of your soundcard. You can then control your synth with code using the midi_* fns and also manipulate the audio using live_audio and FX:

with_fx :reverb, room: 1 do
  live_audio :moog
end
live_loop :moog_trigger do
  use_real_time
  midi (octs :e1, 3).tick, sustain: 0.1
  sleep 0.125
end

(The fn midi is available as a handy shortcut to sending both note on and note off events with a single command. Check out its documentation for further information).