My first drum machine was a Korg Volca Drum, a FM-based drum synthesizer. When Moritz Klein posted this design for a simple FM eurorack drum module, it brought me back to the sounds and textures of the Volca Drum.

Moritz’s design features two analog operators, which can be set to either FM mode (one acts as a modulator and the other as a carrier) or non-FM mode (only one operator directly outputs its waveform to the output). These operators are wave shaped from triangle waves to sine waves, and there is a switch to select pulse waves for more metallic sounds.

There are knobs to control the pitch of both operators, depth of the pitch envelope, decay time of the pitch envelop, decay time of the overall sound, and the level of the pitch CV input. CV inputs include trigger, accent, pitch, and decay.

Once assembled the module creates a wide variety of drum, percussive, and simple synthesis sounds and is a bit of a multi-tool for the drum section.