Best PC Speaker music ever was Xenon II, by Bomb the Bass[0] (which much later I discovered was a re-rendition of Carpenter' Assault on Precint 13 OST[1]).
May sound silly for some people today, but that was some incredible wizardry at the times, given the limitations (PC speaker was monophonic, square-wave only). As a YouTube comment says: "This is musical equivalent to pixel art."
And a great game too!