Small historical correction: Access wasn't the first to figure this out; there was much prior art. Their patent should have been invalidated, but the USPTO has always been horrible when it comes to software. Worse, they used the patent to pressure other companies to not play PWM through the speaker.
What Access *did* do better than others in this area was *background* playback of PWM. They recognized picking timer values that didn't alias with DRAM refresh produced smooth playback, and they stored playback vars in the stack segment for non-volatility and faster access. (SME in this area; AMA)
Yes, I remember one other game pulling a similar trick, some sci-fi racer that digitized a glam rock track over the title screen.
Space Racer (1988)! One of many PC titles that inspired my hobby path.
