So you've got your (insert sound playing program here) cruising at full tilt, and you want to check out this cool Monty Python quote, but you don't want to kill the original sound? This is just the fix, with a little tweaking, of course. =P
The Enlightened Sound Daemon can mix several audio streams into one sound device. It will mix in pre-loaded samples, too. Want to play a frightening sound whenever the user presses the "go" button? No problem, just cache it, and play it back by sample id number.
This is hot off the presses software, get it while it's still hot. It's still got a ways to go yet. Be prepared for a bumpy ride. Any and all reasonable patches and improvements accepted. I expect the communication protocol to change at least once more before it hits 1.0.