Polypaudio is a sound server for UNIX.  It is intended to be an improved
drop-in replacement for the Enlightenment Sounds Daemon (ESOUND).  In
addition to the features ESDOUND provides, polypaudio has:

* Extensible plugin architecture (by loading dynamic modules with dlopen())
* Support for more than one sink/source
* Better low latency behavior
* Embedable into other software (the core is available as C library)
* Completely asynchronous C API
* Simple command line interface for reconfiguring the daemon while running
* Flexible, implicit sample type conversion and resampling
* "Zero-Copy" architecture
* Module autoloading
* Very accurate latency measurement for playback and recording
* May be used to combine multiple sound cards to one (with sample rate
  adjustment)
* Client side latency interpolation

-- Polypaudio homepage

WWW: http://0pointer.de/lennart/projects/polypaudio/