Jack Audio Connection Kit

JACK is the JACK Audio Connection Kit. It was authored by a team of developers headed by Paul Barton Davis, the author of Ardour. It creates a virtual patchbay for connecting different application which have no intrinsic knowledge of each other, as well as communicating time code, tempo, and meter information between applications.

Prerequisites
Although JACK supports many audio system backends, ALSA is recommended, as it provides the most drivers for professional audio cards.

It also requires that a shared memory filesystem mounted at /dev/shm.

From Source
sh ./autogen.sh ./configure make make install
 * Get the latest version from http://jackit.sourceforge.net/download/
 * Configure and build:

Debian and variants
If you are using Debian sarge or newer, you can simply use: apt-get install jackd to install JACK.

Running JACK
Since JACK has a fairly complicated commandline, it is recommended that you use qjackctl to start and stop this.