Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Super Sound - Super Sound is a resourceful audio and music editor.
TwistedWave - TwistedWave is one of the unique audio editors that allow you to edit your music file online without any installation.
Radium - Radium is a music editor with a new type of interface.
Add Audio to Video - Add Audio to Video empowers you to add custom audio tracks to your video files.
SoundEngine - Freeware audio editor/recorder