QMidi

A simple, cross-platform way to support MIDI in Qt. MIDI Output and MIDI File I/O is supported. MIDI output is supported on Windows (Windows Multimedia), Linux (ALSA), Haiku (Midi Kit 2), and macOS (CoreMIDI).

MIDI Output

The QMidiOut class provides an interface to the system's MIDI Out.

/* devices() returns a QMap where the key is the ID and
 * the value is the user-friendly name. */
QMap<QString, QString> vals = QMidiOut::devices();
QMidiOut midi;
midi.connect(/* one of the keys (IDs) from `devices()` */);

There's an easy API for sending messages:

midi.setInstrument(/* voice */ 0, /* instrument */ 0);
midi.noteOn(/* note */ 60, /* voice */ 0 /* , velocity */);
midi.noteOff(/* note */ 60, /* voice */ 0);

Alternatively, you could just send raw MIDI messages:

midi.sendMsg(0x90 + 0 | 60 << 8 | 64 << 16);
/* note on, voice 0; middle C (60); velocity 64 */

Or you could construct a QMidiEvent (from QMidiFile.h) and send it:

QMidiEvent e;
e.setType(QMidiEvent::NoteOn);
e.setVoice(0);
e.setNote(60);
e.setVelocity(64);
midi.sendEvent(e);

Once you're done:

midi.disconnect();

MIDI File I/O

Classes for MIDI file I/O were rewritten from Div's Midi Utilities (homepage | Google Code) from C to Qt/C++.

Quick example:

QMidiFile f;
f.load(" .. some filename .. ");
f.save(" .. some filename .. ");

You can get the events using f.events() which returns a QList<QMidiEvent*>*. For information on using these classes in conjuction with the MIDI output class to play files see the qtplaysmf example in the examples folder.