Doepfer A-178 Theremin CV Source is a theremin module for modular synthesizers in Eurorack format. The module generates a variable control voltage by approaching the hand to an antenna. Furthermore, a gate output is available, which can be set to trigger an envelope generator or a VCA. To emulate the original Theremin, two A-178s, a VCO and a linear VCA are needed. However, it also makes sense to control other functions in the Eurorack system: Filter frequencies, modulations, tempo, on/off times.