Reading this account brought back memories.<p>I had a Tandy 2000 when I was a kid. I tried to get polyphonic sound output out of the thing's beeper via PWM, by taking advantage of the fact that the machine's 80186 CPU had three internal very high res timers in addition to the onboard 8253 timer used to drive the speaker (the same timer is used on the PC, but at different I/O locations; the T2K ran DOS but was one of those rare machines that were NOT "100% IBM compatible"). By grabbing a spare timer, programming it, and setting the cpu to halt until it got a timer interrupt and toggle the speaker line when it did, I was able to get a very rough out of tune approximation of multiple tones, as well as rudimentary volume control.<p>The system clock froze after I ran my experiments but it was worth it... FOR SCIENCE!
I was excited everytime I've heard Mach-3 digitized music back on the PC (DOS) - <a href="http://www.mobygames.com/game/dos/mach-3" rel="nofollow">http://www.mobygames.com/game/dos/mach-3</a> - then later came all mods/s3m/ft/etc. trackers (I did not had Commodore/Amiga/Atari, just PC and Apple ][)
For some reasons this reminds me of the somewhat common hack of soldered together resistors attached to the parallel port used as a simple DAC. Anyone else who burned their fingers doing this?
Slightly off topic -- does anyone remember a boot disk in the late 80's or early 90's that would play voice from the PC speaker, saying something to the effect of, "Help, I'm trapped inside the computer"? I can't remember if it was on my 8088 or something later...
To be fair, playing back MOD files on an XT through a PC speaker _has_ been done before -- pretty sure it was ModEdit, but there might have been something else (also). When I lost my Atari ST and only had an XT it was all I had =)