Mostly just had to work out the notes, then making sure the slowed down parts didn't sound off. The library itself (Tone.js) is very simple to set up and mess around in, at least for the basic stuff.
-Gang Starr / Nujabes blend - https://youtu.be/lsci1vu6ickDOOM Tribute - https://youtu.be/qmBQ2BDefKMDonut of the Heart cover in Javascript - https://youtu.be/afLc2CkC8lk