Granucon - music software - virtual midi keyboard

Virtual MIDI Keyboard Manual - Keyboard commands

In the following table you can find a list of keyboard commands.

Up-Arrow	Increase program number.
Down-Arrow	Decrease program number.
Right-Arrow	Transpose up.
Left-Arrow	Transpose down.
Shift Key (down)	Sends sustain on message to midi out port.
Shift Key (up)	Sends sustain off message to midi out port.

In the following image you can see which keys are used to play MIDI notes.