I reverse-engineered the undocumented Yamaha MODX M .Y2L file format and documented it (plus free browser tools)
Yamaha doesn't document the .Y2L/.Y2U performance format, so I reverse-engineered it from scratch — binary-diffing exports on real hardware, one parameter at a time, a couple thousand test files. Every known user-editable parameter across all four engines (AWM2, AN-X, FM-X, Drum) is now binary-verified, with the structure, encoding and offsets written up in the repo. Every offset is backed by an actual A/B diff.
The thing that started it was wanting to merge performances from multiple libraries without endless clicking on the hardware, so there are also browser tools that came out of the format work — a merger, an early parameter editor, etc.
All local, no install, nothing uploaded, MIT. Hobby project, first GitHub repo, so rough edges exist — test on copies, keep backups, Montage M not fully verified yet. https://github.com/YSFCforge/ysfc-forge
If you're into binary format archaeology or you've looked at this format too, I'd love to compare notes.