JACK Audio Connection Kit

JACK provides a basic infrastructure for audio applications to communicate with each other and with audio hardware. Through JACK, users are enabled to build powerful systems for signal processing and music production. Source: jackaudio.org

Debian packages:

Realtime

jackd is better run with realtime priorities.

Realtime possibilities are included in the mainline kernel, so you don't need a custom kernel.

During installation, jackd2 asks whether you want to modify /etc/security/limits.d/audio to bring realtime priorities to the audio group (which is usually fine for a single user desktop usage).

You can re-run dpkg-reconfigure jackd2 later if you need.

Tools

As a start, you can manage jackd and your audio channels with the qjackctl software.