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
Oceanaudio - Ocenaudio is a cross-platform, easy to use, fast and functional audio editor.
GoldWave - GoldWave. Digital Audio Editing Software. Record • Restore • Convert • Analyze. Fully loaded to do everything from the simplest recording and editing to the most sophisticated audio processing, restoration, enhancements, analysis, and conversions.
Ardour - Record, edit, and mix on Linux, Mac OS X, and Windows.
AudioMass - A full-featured web based audio editor 🎶