In a nutshell, NAS is the audio equivalent of an X display server.
The Network Audio System (NAS) was developed by NCD for playing,
recording, and manipulating audio data over a network. Like the
X Window System, it uses the client/server model to separate
applications from the specific drivers that control audio input
and output devices.
Key features of the Network Audio System include:
o Device-independent audio over the network
o Lots of audio file and data formats
o Can store sounds in server for rapid replay
o Extensive mixing, separating, and manipulation of audio data
o Simultaneous use of audio devices by multiple applications
o Use by a growing number of ISVs
o Small size
o Free! No obnoxious licensing terms