GNU LilyPond: One of the best-known and most ambitious music programs for Linux is the LilyPond score engraving system.

• makes beautiful prints, seeks to to revive the aesthetics of traditionally engraved music through automated engraving engine
• easy to type, text based input
• extensive documentation, including tutorial and a glossary of musical terms for non-native English speakers
• prompt support by heavy development and active user community
• ready to print music scores from the Mutopia Project
• import filters: abc2ly, etf2ly (Finale), midi2ly, mup2ly, musedata2ly and xml2ly
• supported by the printing engines of NoteEdit, Rosegarden and Denemo
• Emacs and VIM editing modes