JACK is system for handling real-time, low latency audio
(and MIDI). It runs on GNU/Linux, Solaris, FreeBSD, OS X and
Windows (and can be ported to other POSIX-conformant
platforms). It can connect a number of different
applications to an audio device, as well as allowing them to
share audio between themselves. Its clients can run in their
own processes (ie. as normal applications), or can they can
run within the JACK server (ie. as a "plugin"). JACK also
has support for distributing audio processing across a
network, both fast & reliable LANs as well as slower, less
reliable WANs.