Virtual MIDI Piano Keyboard is a MIDI event generator and receiver. It
doesn't produce any sound by itself, but can be used to drive a MIDI
synthesizer (either hardware or software, internal or external). You can use
the computer's keyboard to play MIDI notes, and also the mouse. You can use
the Virtual MIDI Piano Keyboard to display the played MIDI notes from
another instrument or MIDI file player. To do so, connect the other MIDI
port to the input port of VMPK.