This device is a self contained synthesizer built into an IBM joystick (circa 1984). Because of the simplicity of the original construction, it was quite simple to 'hack' the joystick control to interface with my circuit. Essentially the two axis of the joystick controls two 1 mega-ohm potentiometers. There is also a momentary button which triggers the amplitude envelope. It's fun to play and has lots of expressive potential.