JACK is a professional sound server

Sound server

A sound server is software that manages the use of and access to audio devices, most notably, the soundcard. It usually runs as a background process...

 daemon

Daemon (computer software)

In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...

 that provides real-time, low latency

Low latency

Low latency allows human-unnoticeable delays between an input being processed and the corresponding output providing real time characteristics. This can be especially important for internet connections utilizing services such as online gaming and VOIP....

 connections for both audio and MIDI data between applications that implement its API. It is under constant development by a community of open source developers led by Paul Davis

Paul Davis (programmer)

Paul Davis is a British software developer best known for his work on audio software for the Linux operating system, and for his role as one of the first two programmers at Amazon.com....

 (who won an Open Source Award in 2004 for this work) and has been a key piece of infrastructure and the de-facto standard for professional audio software on Linux since its inception in 2002.