Playable theremin in VRChat Udon, programmed in UdonSharp.
The interesting class is Assets/UTheremin/UTheremin.cs. It synthesizes the waveform in realtime;
Unfortunately, udon computation is very slow, so the most you can synthesize is about 256 samples
every frame, so the max sampling rate for realtime audio is practically limited to <6000Hz.
You'll need to install the VRCSDK3 and UdonSharp unitypackages manually.