[From the EsounD website:]

[W]hen two or more applications want to play sounds at the same time,
it's on a first-come, first-served basis. Whoever gets to the audio
device first wins. EsounD changes all of that...

The Enlightened Sound Daemon mixes several audio streams for playback by
a single audio device. You can also pre-load samples, and play them back
without having to send all the data for the sound. Network transparency
is also built in, so you can play sounds on one machine, and listen to
them on another.

WWW: http://www.tux.org/~ricdude/EsounD.html