slackbuilds/audio/jack-keyboard/README

jack-keyboard (virtual MIDI keyboard)

jack-keyboard is a virtual MIDI keyboard - a program that allows you to
send JACK MIDI events (play ;-) using your PC keyboard. It's somewhat
similar to vkeybd, except it uses JACK MIDI instead of ALSA, and the
default keyboard mapping is much better - it uses the same layout as
trackers (like Impulse Tracker) did, so you have two and half octaves
under your fingers.

Optional dependency: lash. By default, this is autodetected. If you want
to disable building with lash, set LASH=no in the script's environment.

This package 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 disable
capabilities, pass SETCAP=no to the script.