Norbert Kehrer released a music tool for the Commodore C64. With his program YM-64 you can play music files on the Commodore C64 that were made for Atari ST, Amstrad/Schneider CPC, Sinclair ZX spectrum or MSX computers. All these computers had a YM2149 or AY-3-8910 music chip that had a square wave sound in three channels. It had a noise generator, which could be mixed with the the three square wave channels, and a parameter controllable envelope generator.