This is very cool!

Some things were broken for me(On Firefox 65.0.1, Ubuntu 18.04):

* Pause button doesn't immediately pause, the current note(?) ends over a period of time before pausing

* Fullscreen, and a few other buttons don't work. Also, I can't tell if my mouse click even registered on the button

Very interesting project nonetheless, and the music generated is quite nice to listen to. I particularly like how well placed the silences are. The percussion does need some tuning, like you've mentioned.