As recommeded by several above, Lilypond is worth a look. See some slightly more complicated examples in the Lilypond docs at: http://www.lilypond.org/doc/v2.12/Documentation/user/lilypond/Common-notation-for-vocal-music#Common-notation-for-vocal-music

There is this now. http://www.microsoft.com/security_essentials/

Oops. Try http://www.boardgamegeek.com/image/134580 if you're interested.