Driver needs to be abstracted out further
Driver has become an unmaintainable mess, and it will only get worse as support for new MegaMods is added. I think it'd be worth rewriting it so each type of MegaMod is in its own file, with some shared code for outputting to the bus, etc. Might even make sense to do a file for each chip and one for each mod, and the mod would be responsible for setting up mappings between VGM commands and chip outputs... would make it a lot easier to handle edge cases like playing 2xOPN tunes on OPN2.
This should probably also be done with the channel muting UI and channel LED manager. With some of the proposed LED changes it would make more sense for the interface between driver and the LED code to be via raw LED brightness values, rather than the channel on/off/update bitmask that it uses currently.