Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
LMMS - Make music with a free, cross-platform tool
Reaper - Reaper is a focused digital audio workstation (DAW) developed by Cockos. In the creation of the software, the digital audio technology company intended to make audio editing accessible to the masses.
Oceanaudio - Ocenaudio is a cross-platform, easy to use, fast and functional audio editor.
GarageBand - GarageBand is a fully equipped music creation studio for Mac
Ardour - Record, edit, and mix on Linux, Mac OS X, and Windows.