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:
jackd2 (jackd is a dummy package)
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.
Useful links
https://www.linuxaudio.org/resources.html : linux audio community with documentation and more