This simple interface allows MATLAB to read incoming MIDI data from a MIDI device or another MIDI program. For instance, if a MIDI keyboard is connected to the computer running MATLAB, this interface could be used to see what keys the user is playing, what knobs he's twisting, what pedals he has down, etc.
% Open an interface; the tool will prompt to select a device.
midi_interface('open');

% Play some notes on a connected keyboard or wiggle some knobs on a MIDI controller.

% Read all the new MIDI messages.
messages = midi_interface();

% Close the device.
midi_interface('close');

This currently only works on Windows (32/64-bit) and only supports one MIDI device at a time. If this tool proves useful for people, we could take it further, so just let me know!

Early beta.