SlackBuildsOrg/audio/setBfree

MIDI-controlled, software synthesizer designed to imitate the sound
and properties of the electromechanical organs and sound modification
devices that brought world-wide fame to the names and products of
Laurens Hammond and Don Leslie. 

Optional dependencies are lv2,liblo and ftgl to build the
standalone and lv2 OpenGL UI:
For the LV2 GUI you need a LV2 host with Gtk support, like jalv.
jalv.gtk -l ~/.config/setBfree http://gareus.org/oss/lv2/b_synth

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.