Musical score format used by Guitar Pro 3, a music composition program for guitar and other plucked string instruments; contains tablatures for guitar, bass, or banjo; used for creating scores that can be played back using MIDI data or printed to a hard copy.
Program(s) that open gp3 files
Mac / Windows: Arobas Music Guitar Pro 3 or later
Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/gp3
