Ardour is a full-featured, free and open-source hard disk recorder and digital audio workstation program suitable for professional use. It features unlimited audio tracks and buses, non-destructive, non-linear editing with unlimited undo, and anything-to-anywhere signal routing. It supports standard file formats, such as BWF, WAV, WAV64, AIFF and CAF, and it can use LADSPA, LV2, VST and AudioUnit plugin formats.
Ardour runs on Linux and Mac OS X, and uses the Jack Audio Connection Kit (JACK) to interface with the computer's sound card, as well as with other audio applications running on the same system.
More information on Ardour can be found at http://ardour.org/.