Virtual Audio Cable - Ever wanted to record your speaker output? (loopback) This is for you.
Super Sound - Super Sound is a resourceful audio and music editor.
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!
MixPad - MixPad is free music Music Mixer and Recording software designed for easy audio production.
JACK Audio Connection Kit - JACK Audio Connection Kit|Home
Audio Video Editor and Mixer - Audio Video Editor and Mixer is a tool that helps you add changes to your video and audio files.