Virtual MIDI Piano Keyboard is a MIDI events 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.

Optional: Jack-audio-connection