https://pm.revision-party.net/releases?competition_id=13
The final result is in the file petersalomonsen_wasmmusic.html.
The uncompressed HTML and JS file can be found in song.html and main.js.
The Wasm file was compressed to png using encodewasm.py and encoded as base64 before inserting into the HTML file. Decompressing is done by rendering the png to a canvas.
For this player simple chaining of audio chunks was done on the main thread. Normally this is more stable when done using AudioWorklet.
The Wasm file was exported from the WebAssembly music studio, where you can create the sequence in JavaScript and Synth in AssemblyScript.
The source for this particular song can be viewed, edited and played here:
https://petersalomonsen.com/webassemblymusic/livecodev2/?gist=d71387112368a2692dc1d84c0ab5b1d2