Qtractor is free and open source Audio/MIDI multi-track sequencer. It support Linux platforms with Jack Audio Connection Kit (JACK) for audio, and the Advanced Linux Sound Architecture (ALSA) for MIDI.
Qtractor is a great software to edit and apply effects to multi-audio files and MIDI files. It support several audio files formats such as OGG, MP3, FlAC, AIFF, wave and many more.
Qtractor comes with really simple and organized graphical user interface, you will find it quite simple to use at the first time. Also, here’s a quick start guide and user manual you can download for further information.
Install Qtractor 0.5.7 on Ubuntu 12.10 Quantal Quetzal and Ubuntu 12.04 LTS Precise Pangolin
Run Terminal “Ctrl+Alt+T” then type,
sudo apt-add-repository ppa:kxstudio-team/ppa
sudo apt-get update
sudo apt-get install qtractor
Thanks to KXStudio PPA.
Download page for other Linux distributions.
Official page for Qtractor.