[youtube]http://www.youtube.com/watch?v=FQjIO_K0QUM[/youtube]
Sorry for too long preface/introduction ;) but it was my very _first_ contact with ZXpand module for ZX81 computer (32Kb or RAM, SD-card instant loading plus additional AY-interface in standard of classic ZX81’s ZonX AY-interface from 80s).
It is really ZX81 playing music via AY chip (well, actually its Japanese version: YM). You can get both modules from RWAP Software: http://www.rwapsoftware.co.uk/zx812.html
via ZX81 computer with AY-interface & ZXpand Module. – YouTube.