CoreMIDI

(require (planet evhan/coremidi))

This module provides a minimal interface to Apple’s CoreMIDI library.

It provides for the creation & destruction of MIDI connections and for the following MIDI messages: Note On, Note Off, Program Change, and Aftertouch.

1 MIDI Connections

In order to send MIDI messages anywhere you must first create a MIDI connection:

(midi-open  [ destination-n             client-name             port-name])   →   midi-connection?

destination-n : integer? = 0

client-name : string? = "rkt client"

port-name : string? = "rkt outport"

Opens a midi-connection to the destination-nth available MIDI destination (as provided by the CoreMIDI system), or the first available destination if no destination-n is given. client-name and port-name can optionally be the identifiers assigned to the new midi-connection’s internal components within the CoreMIDI system. For most purposes you can ignore these names.

midi-connection handles will remain open until closed:

(midi-close midi-destination) → void?

midi-destination : midi-destination?

Destroys a midi-connection (previously created with midi-open).

2 MIDI Messages

The following MIDI messaging procedures all take a midi-connection as a first argument. This will be the destination to which the message is sent.

(note-on midi channel note [velocity]) → void?

midi : midi-connection?

channel : integer?

note : integer?

velocity : integer? = 64

Sends a MIDI Note On signal to the given midi-connection on the given channel. note is the MIDI note number and velocity is optionally the note’s velocity. Both are integers from 0-127.

(note-off midi channel note [velocity]) → void?

midi : midi-connection?

channel : integer?

note : integer?

velocity : integer? = 64

Entirely mimics note-on’s functionality, except that it sends a MIDI Note Off message instead of a Note On.

(aftertouch midi channel note touch) → void?

midi : midi-connection?

channel : integer?

note : integer?

touch : integer?

Sends a MIDI Aftertouch signal to the given midi-connection on the given channel. note is the note value and touch is the weight of the aftertouch. Both are integers from 0-127.

(program-change midi channel preset) → void?

midi : midi-connection?

channel : integer?

preset : integer?

Sends a MIDI Program Change signal to the given midi-connection on the given channel. preset is the program number from 0-127.

3 Example

Here’s a simple example making use of most of the functions defined above. It simply plays a C major scale at 60 bpm.

(define (play-each notes)

(define midi (midi-open))

(program-change midi 1 0)

(for/list ((note notes))

(note-on midi 1 note 120)

(sleep 1)

(note-off midi 1 note))

(midi-close midi) (void))

(play-each '(60 62 64 65 67 69 71 72))

Please let me know of any bugs you encounter.