WIP #picotron waveshaping & envelopes (thx @luchak for the idea of going hard cut -> foldback)

https://youtu.be/UZ9YIaLpWmA

PFX6416 Synthesizer Test

YouTube

@zep This is incredible. I never thought I'd hear a Lexaloffle synth sounding _filthy_ but I love it.

At least from the UI, it looks like you're going with sinusoidal foldback rather than linear/triangular? I didn't experiment with that but I expect it probably sounds a little cleaner, or doesn't introduce quite as much energy in new harmonics?

@luchak I'm very happy to hear that! One reason Picotron exists is that I couldn't bend the PICO-8 synth to sound filthy enough for Voxatron, haha

The sinusoidal foldback is cleaner, but maybe /too/ clean in some cases, so it might end up being a toggle-able flag.