LilyPond is a music typesetter.  It produces sheet music using a
high-level description file, which is plain text, as input.  You
can use your favorite text editor to enter the description files.
The font and the layout were inspired by engraved music, but can
be modified.  The program also has limited MIDI functionality: you
can write MIDI files, and there is a MIDI to lilypond conversion
tool, midi2ly.  Conversion tools for PMX, MUP, ABC, Finale and
Musedata are also included.

WWW:  http://lilypond.org/web/

Trevor Johnson