Other sound stuff can be found at http://absolutevalueofnoise.ca/ or https://absolutevalueofnoise.bandcamp.com/
I do noise art and sound art.
As for the code .. if you left click the itch game page with your mouse just a little outside of the bitsy-game box, you should be able to look at the source code for the frame (or iframe). Down at the bottom of the bitsy html code is a section called "DOCUMENT BODY". Inside the body is a canvas tag called "game". That's your bitsy square. You can add whatever you like above and below it .. or even on the sides if you want to be fancy. For the audio I simply use the html5 "audio" tag with autoplay and loop turned on.