Very curious about the music side of things, SGB music has seemed like a black box. Is the conversion .MOD/tracker-based by any chance?
I have mostly worked on the data injection side of things and less on the composition part. I haven't quite decided what format would work best, but I already have a partially working external script that can convert MIDI, sort of. There's some limitations with MIDI though. I have briefly looked at SNES GSS and I'm still figuring out if I might be able to use its exported data.