A discussion about the Web Audio API from a couple of weeks ago with the title "I don't know who the Web Audio API is designed for": https://news.ycombinator.com/item?id=15240762

I'm still not convinced that this API is actually useful for any application that needs to play sound or music, but it definitely seems to have the "interesting synthesizer experiments" segment covered.

https://inverted3.gitlab.io/drum-machine/ is a working multi channel drum machine using Web Audio.

floatboth

There are a few trackers too:

https://github.com/steffest/BassoonTracker

https://github.com/mbitsnbites/soundbox

https://github.com/pgregory/wetracker

Also, I wrote a WebExtension that lets you apply pan and gain to audio in YouTube videos (and other videos that are not cross-domain) using Web Audio https://addons.mozilla.org/en-US/firefox/addon/soundfixer/