Super Sound - Super Sound is a resourceful audio and music editor.
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Add Audio to Video - Add Audio to Video empowers you to add custom audio tracks to your video files.
GarageBand - GarageBand is a fully equipped music creation studio for Mac
Adobe Audition - Mix, edit, and create audio content in Adobe Audition CC with a comprehensive toolset that includes multitrack, waveform, and spectral display.
Audio Video Editor and Mixer - Audio Video Editor and Mixer is a tool that helps you add changes to your video and audio files.