Qtractor

Its author is Rui Nuno Capela, who is also responsible for the Qjackctl, Qsynth and Qsampler line of Linux audio software.

Released under the terms of the GNU General Public License, Qtractor is a free and open-source software application.

Qtractor is a non-destructive digital audio and MIDI multi-track composition sequencer and arranger software application.

Exceptions are files resulting from capture and recording operations or from explicit changes made through specialized Clip editing (e.g., MIDI Editor).

Qtractor is natively hardwired and exclusive to the JACK Audio Connection Kit infrastructure, and the ALSA sequencer for MIDI.