Pulse width modulation of the PC speaker was also a thing back in the 1990s. ModPlay under DOS could use the PC speaker as an output to play back Amiga MOD fil

Pulse width modulation of the PC speaker was also a thing back in the 1990s. ModPlay under DOS could use the PC speaker as an output to play back Amiga MOD files, although it was very quiet. I ended up making a bunch of parallel port DACs in high school for friends so they could play MODs with a higher sound quality. Good times!