The first is an example for creating a WebAudio patch with Rust. Unfortunately it doesn't use custom processing function, just puts together the standard WebAudio API components. And so we have the second project which is a C++ example of submitting a custom AudioWorkletProcessor ; it was working both in Firefox and Chromium for me, so perhaps the API is already stable enough to give it a try.
Meanwhile, progress is made with getting Scala Native to compile to wasm:
What I would like to figure out is if I can write an AudioWorkletProcessor function in Scala this way.