Pro Tools (Mac)
From Just Solve the File Format Problem
Early Pro Tools digital audio workstation software for Macintosh, versions 3-5 used a session file format which uses the Resource Fork only of the Mac's HFS file system. It was replaced with PTS Pro Tools 5.1-6.9. It is a session file which doesn't directly contain the audio data, but should be accompanied by audio files (such as SD2).
