Caustic Song file (optional):
Today I was messing around in the modular synth having played around a lot with VCVRack (amazing free eurorack modular synth program - if you've never heard of it, you probably should have a look)
I was once again bemoaning Caustic's lack of a simple knob module, but realized that I could actually optimize my envelope into mixer trick such that the envelope is fully usable for other things, and so you only need an single mixer module on top of an envelope to add a constant output CV.
Then I tried feeding back that constant CV into a mixer, originally to try and get higher CVs than I could otherwise - my aim here was to produce an LFO slower than the Mini LFO, and I succeeded at that, which is cool and all... but if you feedback a mixer into itself at just the right amplitude levels, in Caustic it starts to self-oscillate!
Even more interesting, since it's approximating a dirty short cycle square wave, if you're very gentle on the incoming trigger signal, you can actually pitch it up and down depending on that triggering seed signal.
I've (hopefully) attached a caustic file - slightly twiddle the input 1 volume on the row 3 column 3 mixer to pitch the sound up and down... and then note there's not a single proper oscillator anywhere in the patch!
No idea whether it tracks accurately or even what Caustic's 'voltage' per octave system is, but it's a fun little thing!