Useful software

PDF
Adobe Acrobat Reader Windows - Macintosh - Linux

Scores Editors
Finale Windows - Macintosh

MusiXTeX and Related Software Linux/Unix - MS-DOS - Windows - MAC OSX
LilyPond, music notation for everyone GNU/Linux - MacOS X/Fink - Windows - FreeBSD - NetBSD
Encore Windows - Macintosh
Capella
Sibelius Windows - Macintosh
MusEdit
notation Braille
Notation Software, Inc.
Myriad Software Windows - Macintosh

MP3
Real One Player Windows - Macintosh
QuickTime Windows - Macintosh
WinAmp Windows - Macintosh
Windows Media Player Windows

MIDI
Real One Player Windows - Macintosh
QuickTime Windows - Macintosh
WinAmp Windows - Macintosh
Windows Media Player Windows

Games music theory and solfege
eLuna Ear Training eLuna Ear Training est un logiciel dont le but est de permettre un travail de l'oreille, et qui s'adresse donc principalement aux musiciens.
GNU Solfege Solfege is free music education software. Use it to train your rhythm, interval, scale and chord skills. Solfege - Smarten your ears!
Happy Note! With Happy Note!, you can read music notes and learn music theory and solfege as if they were a game. Actually, with Happy Note! music theory IS a game, or more exactly a series of computer games.
De vrais jeux vidéo à télécharger pour apprendre la musique et le solfège en s'amusant !

Guitar Tablature Editors
PowerTab Windows
TablEdit Windows - Macintosh
TEFView Windows - Macintosh

Lute Tablature Editors
Django lute guitar tablature software Windows
Download the free demonstration version of Fronimo Windows
Tab Linux/Unix - MS-DOS - Windows - MAC OSX