There's a good start at it in the tree ( https://github.com/mamedev/mame/blob/master/src/mame/yamaha/ymqy70.cpp https://github.com/mamedev/mame/blob/master/src/

There's a good start at it in the tree ( https://github.com/mamedev/mame/blob/master/src/mame/yamaha/ymqy70.cpp https://github.com/mamedev/mame/blob/master/src/mame/yamaha/... ) but it's missing the sound generation which is kind of the important part :-)