Ardour is a professional, full-featured hard disk recorder and Digital Audio Workstation (DAW). Ardour is Free/Libre Open Source Software (FLOSS).
PLEASE NOTE: This link refers to an older version of Ardour (3.5). To read the updated tutorial for Ardour 4, go to http://brunoruviaro.github.io/ardour4-tutorial/
More information on Ardour can be found at http://ardour.org/.