I have added sound! After the #Wozamp project, I couldn't settle on manually tickling $C030, so I've tested a thing.
I can play samples at 8kHz with a precision of 7 bits... As long as they're very very short to fit in memory.
The sound player and samples are generated by C code.
Commit: https://github.com/colinleroy/a2tools/commit/db409caccc53b2298719ea159d1d5a8d9b36f47d