SlackBuildsOrg/audio/qjackctl

Provides a simple GUI dialog for setting several JACK daemon
parameters, which are properly saved between sessions, and a way
control of the status of the audio server daemon. With time, this
primordial interface has become richer by including a enhanced
patchbay and connection control features.

Note:
This package optionally uses POSIX filesystem capabilities to execute with
elevated privileges (required for realtime audio processing). This
may be considered a security/stability risk. Please read
http://www.slackbuilds.org/caps/ for more information. To enable
capabilities, pass SETCAP=yes to the script.

Optional dependency: portaudio and jack2