first best software is
Ardour:
(http://www.ardour.org/)
2nd
Audacity:
(http://audacity.sourceforge.net/)
3rd
Grip:
(http://nostatic.org/grip/)
Hydrogen:
(http://www.hydrogen-music.org/)
Hydrogen is an advanced drum machine for GNU/Linux. It's main goal is to bring professional yet simple and intuitive pattern-based drum programming.
Jokosher:
(http://www.jokosher.org/)
Jokosher is a simple and powerful multi-track studio. Jokosher provides a complete application for recording, editing, mixing and exporting audio, and has been specifically designed with usability in mind.
The developers behind Jokosher have re-thought audio production at every level, and created something devilishly simple to use.
LMMS:
(http://lmms.sourceforge.net/)
LMMS aims to be a free alternative to popular (but commercial and closed- source) programs like FruityLoops/FL Studio, Cubase and Logic allowing you to produce music with your computer. This includes creation of loops, synthesizing and mixing sounds, arranging samples, having fun with your MIDI-keyboard and much more...
MusE:
(http://www.muse-sequencer.org/)
MusE is a MIDI/Audio sequencer with recording and editing capabilities written by Werner Schweer. MusE aims to be a complete multitrack virtual studio for Linux.
Midi sequencing
Record/Playback/Import
Input filter
Audio sequencing
Record/Playback several mono/stereo inputs/outputs.
AudioGroups
LASH
Perform audio effects like chorus/flanger in realtime!
Jack - jack-audio-connection-kit
Use the jack for midi/audio routing.
Internal Audio Routing Interface
ALSA - based on the Advanced Linux Sound Architecture
You can use several soundcards to access external midi devices and record/playback them with MusE.
Rosegarden:
(http://www.rosegardenmusic.com/)
Rosegarden is a professional audio and MIDI sequencer, score editor, and general-purpose music composition and editing environment.
soundKonverter:
(http://www.kde-apps.org/content/show.php?content=29024)
soundKonverter is a frontend to various audio converters.
The key features are:
Audio conversion
Replay Gain calculation
CD ripping
Streamripper:
(http://streamripper.sourceforge.net/)
hope this will not disappoint u