A fast multi-track audio editor and recorder for Linux, BSD, Mac OS, and Windows. The source code for Audacity is released under the GNU General Public License. Supports WAV, AIFF, Ogg, and MP3 formats and comes with a neat and intuitve graphical user interface.
Features include Multi-track mixing, a lot of digital built-in effects and effect plug-ins, envelope editing, mixing, all with unlimited undo. You can export your files as .wav, .mp3 or .ogg.
The current stable version of Audacity is 1.2.4.