libao

Libao is a cross-platform audio library that allows programs to output audio using a simple API on a wide variety of platforms. It currently supports:

Null output (handy for testing without a sound device)
WAV files
AU files
OSS (Open Sound System, used on Linux and FreeBSD
ALSA (Advanced Linux Sound Architecture)
polypaudio (next generation GNOME sound server)
esd (EsounD or Enlightened Sound Daemon)
AIX
Sun/NetBSD/OpenBSD
IRIX
NAS (Network Audio Server