FM Percussion Module

The FM Drum is a percussion module designed to make far-out and strange sounds. It features a manually controlled modulating oscillator and a voltage controlled oscillator. Each oscillator has both square and triangle waveshapes, selectable with toggle switches. It also accepts external CV for modulation. It is easy to patch, just input a trigger or gate source and out comes a new sound.

http://www.bartonmusicalcircuits.com/fmd/