You can use my ArcadeMIDI extension - it has instructions on how to convert a MIDI file (which you might be able to obtain by writing a score in a music notation software and exporting it as a MIDI file, or downloading it off the internet) to the pictures used by the extension.
I also believe I have already done Megalovania before, but with an older extension or raw JavaScript code generation. (I don’t remember…it’s getting hard to keep track of stuff lol…) Try searching the forums.