The engine will now load json files generated by the toneJS MIDI converter. I've posted the source on GitHub, with a debug build of the game that automatically loads and plays "music.json". The sound quality was pretty horrendous with the test MIDI I used, but it wasn't an 8-bit track, and was probably never meant to be played with just frequency and duration. Have a look and see if whatever music you're planning to produce for the jam will sound ok. I also want to say thanks to HeavyPixels for providing this great resource.
https://github.com/LucidaDragon/Ninja/tree/master/SmolGame/bin/Debug