The Jack Audio Connection Kit

JACK is a low-latency audio server, written primarily for the Linux
operating system. 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 a
normal application), or can they can run within a JACK server (ie. a
"plugin").

JACK is different from other audio server efforts in that it has been
designed from the ground up to be suitable for professional audio
work. This means that it focuses on two key areas: synchronous
execution of all clients, and low latency operation.