I know this is an old thread , but I've been working on a Dual sid + FM ( 3526 and 3812 ) music driver for a while now. Should have something out there very soon. Also in the process of modifying the C64 version of Bubble Bobble to play the actual arcade music if you have both a Commodore 128 and the FM cart. I did find complete documentation for the FM chips and the writing/reading technique as used by you guys is correct.
Will keep you progress posted,
Gaz.
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