> Oh gosh. Is that really what DOS games used to sound like?

If you only had a PC speaker, yes, although some games sounded better. At some point in the 90s, Sound Blaster cards started getting popular and those sounded way better than this example.

PC's didn't have any dedicated sound hardware (unless you had a sound card), so any kind of sound/music playback would have to be done in real-time on the CPU, which didn't leave much for the rest of your game. C64, Amiga, etc. all had dedicated sound chips which could do a lot of the synthesis and mixing without burdening the CPU. (This is the same reason why PCs didn't get side-scrolling games until much later than consoles: consoles had dedicated hardware for scrolling tilemaps and displaying sprites, while PCs just had a memory-mapped framebuffer of pixels.)