So, in addition to my game projects, I am taking little bites out of documenting the SKCTL=$8B AUDCTL=$41 Distortion $4x settings at 15 khz. The major table is of course the ones where AUDF1 is not a mod 5 or 15. This has enough guitar sounds to where dozens of timbres (and note tables) are possible, and the octave range for such will reach into the 5th octave without tuning errors.
Once I have this table, I'll write a utility in TurboBASIC that will let you build your own note tables from the listed frequencies. This should be fun. Once built, thanks to @VinsCool, they can be hacked into RMT, hopefully.
Other tables are:
AUDF1 is mod 5. This is the "Fuzzy C" setting, where C distortion frequencies are played in channel 2, and the mod 15 frequency in 1 introduces a fuzzbox
AUDF2 is mod 5. Distorted guitars which will hit intermittently depending on polycounters
AUDF1 is mod 15. Alien crunch sound fx
After that, the same must be done to the equivalent setting in AUDCTL=$40 (i.e. standard 64khz clock). I think once I have both these in the bag, I will write out an extensive doc which documents the various tables in these settings and how to use them.