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.
Oceanaudio - Ocenaudio is a cross-platform, easy to use, fast and functional audio editor.
Add Audio to Video - Add Audio to Video empowers you to add custom audio tracks to your video files.
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.
AudioMass - A full-featured web based audio editor 🎶