Not specifically musical, but beautiful hacking nevertheless...
Dissecting Voice Synthesizers
How to generate exactly the frequencies you want!
Elektron SPS-1 Hacking
The file format of the step mod explained!
Roland SP-808 Hacking
Cartidge Expansion spec, OS disassemblies, disk format, etc. Plus
parameters and commands for the Ensoniq Mirage and Sysex implementation,
and reverse-engineered schematics, etc.
Ensoniq Mirage Hacking
More technical info than you can believe about these synthesizers.
Ensoniq ESQ and SQ80 Hacking
All the technical info we can get on the Ensoniq ASR-X!!!
Ensoniq ASR-X Hacking
Technology Vulturing the MOTU MIDI Time Piece. An interesting
page.
MOTU MTP2 Hacking
Modified, Enhanced Lexicon JamMan software!
Lexicon JamMan Hacking
Okay, not exactly hacking, but still extremely useful and
hard-to-find info. Sysex and MIDI implementation for Korg Poly-800
Korg Poly-800 Hacking
Hacking the Peavey SP (Coming Soon!)
Peavey SP Hacking