Multichannel/unusual PC speaker music

interesting find. Those 3 tunes reminds of some ZX music to some extends.

The list slowly getting longer. Meanwhile, I had thoughts on the matter (not looking to the code, though), and here is what I think so far.

For oldest PCs that runs pure DOS, like XT/AT/386 maybe, the usual timed code approach may be viable, with a delay in the main loop that automatically gets adjusted at startup by measuring actual CPU speed. What is possible to do is limited by the speed of the slowest targeted system with shortest possible delay. So basically a little bit less than a 4.7 MHz 8088 can do, which is the same ballpark as ZX Spectrum. Engine types would be not limited in this case, all approaches should work. Music playing would stop everything else.

However, considering how vastly different PCs and their speeds are, plus the possiblity to run something in background, and that every PC has 8253 PIT to generate interrupts, more universal apporach would be to utilize the interrupts. Now we can have quite good sound loop sample rate (when it runs on a PC that is fast enough), but sound generation methods gets limited. We can either use one-change per loop engines, such as Squeaker or Octode, or PWM like with one pulse at a time (basically the PCM playing trick, just without PCM).

One issue with developing this field is that DosBox isn't terribly accurate in regards of timings and PC Speaker emulation. Considering that Pinball Fantasy sounds reasonable while many of the games listed above is not, I think that the second approach is more accessible at the moment - unless you want to work strictly with old hardware and old tools.