Caustic Song file (optional):
... or something or other...
Basically the controller machine sends the same notes to the source (in this case the bassline), and the pcmsynth. The source produces the sound and the filter modulates it via sidechaining. What's key here is the sample length in the pcmsynth.The idea is to modulate the source while matching it's fundamental frequency. So I'll spare the nerdy math for now, but it works out that a C4 single cycle is 169 samples, +5cents... or as close as I think we can get it at 44100khz.
The sample can be anything, but we want it to match the fundamental frequency, atleast for a starting point. From that point, pretty much everything can be tweaked. The bassline and sample I used are only for example. Notice I also tweaked the pitch and cents knob in the pcmsynth. You could also adjust the start and end point of the loop, tweak the envelope and the lfo, etc. I would avoid changing the polyphony above 1 though or else you'll end up amplifying the signal and it'll get ugly.
The aux modular isn't really necessary. I just put that in to free up the insert slots for the source. Just move the compressor to the source machine and turn it's mixer volume up and you can delete the aux modular.
I also included each of the 4 basic wave shapes in four different pcmsynths in the lower rack to get started.
And if you're thinking it might be nice to drop this setup into any song, you can do that with Mike's app Caustic Guide and here's a group file I created for that. (minus the extra pcmsynths)