Ardour is a great digital audio application. It is completely free and is geared towards professionals. It was released in 2004 and is licensed under GNU general public license. The main author is Paul Davis. Ardour works on Linux and Mac OS. You can record, mix, edit, and master audio files in many different formats. Plugins are also available to give you additional audio effects. It is a hard disk recorder and is capable of variety of tasks. You can import and export part or full sessions in 30 different audio formats. If you would like a professional digital workstation than check out Ardour.