MuseScore is a free cross platform WYSIWYG music notation
program, licenced under GNU GPL. Features:

 - WYSIWYG design, notes are entered on a "virtual notepaper"
 - TrueType font(s) for printing & display allows for high quality
   scaling to all sizes
 - Easy & fast note entry
 - Many editing functions
 - MusicXML import/export
 - MIDI (SMF) import/export
 - MuseData import
 - MIDI input for note entry
 - Integrated sequencer and software synthesizer to play the score
 - Print or create pdf files

This package partially installs to /opt/MuseScore