Generic Midi allows synthesizers and other devices communicate with Ardour. MIDI devices can send commands relating to playback (such as play or stop), performance (such as volume, play, stop, and almost any other function (such as Edit, or Undo).

Many MIDI control surfaces use predefined MIDI protocols such as the "Mackie Control Protocol". In such cases it is best to use Ardour's implementation of that protocol as it is likely more feature complete.