Made a (more polished) playable theremin in Udon:

https://streamable.com/ltzb3n

It can actually generate a few different waveforms besides a pure sine wave, but since udon is so slow, it can only generate about 300 samples per frame, so the max sampling rate is around 6kHz, and all the harmonics alias in weird ways.

https://vrchat.com/home/launch?worldId=wrld_92cc8bc1-10c8-4291-9ed9-6f0378c3bb89

While more complex synthesis isn't feasible, you can load in pre-recorded samples and use an AudioClip as a high-resolution timer (much better than Update() or Animations). My next project is a sequencer/loop machine that syncs at a 4 bar interval, so in theory you can do jam sessions despite internet lag, a la ninjam or jammr. With a few basic instruments like a drum set, xylophone, guitar maybe. I think a chords-only accordion might work in VR too, or a saxophone.