Oops, i forgot to put the concept of the tom module on this site.. by the time it's already finished, anyway... The sound source is a 'true' sine wave oscillator.
This means that the sinewave is generates using a 18dB/oct filter made to resonate permanently. On other synth vco's sine wave are sometimes generated by 'bending' a triangle-wave into a sine wave. The difference between a true sinewave oscillator and a 'bent' sine-oscillator is only noticeable in fast frequency modulation. Due to it's nature the sinewave gets asymmetric generating overtones. I wanted a very clean sounding tom (as a counterweight to the more rough sounding bassdrum) so i realized a true sinewave oscillator. Frequency and volume can be/is modulated with two decay-only envelopes..
p.s. for sake of simplicity and layout esthetics (see post below) i omitted the distortion unit, that anyway contradicts the paradigm of a clean sounding tom