Canorus is a free cross-platform music score editor. It supports an unlimited number and length of staffs, polyphony, a MIDI playback of notes, chord markings, lyrics, import/export filters to formats like MIDI, MusicXML, ABC Music, MusiXTeX and LilyPond
VocalEasel is a simple lead sheet editor and music rehearsal tool designed for the needs of Jazz vocalists, using LilyPond to produce printable lead sheets and MMA (Musical Midi Accompaniment) to produce MIDI accompaniments.
apecomment is an APEv2 music tag editor. It will also support ID3v1/v2 writing. Features other editors do not have are: 1) support encoding detection/conversion, 2) file attachment (cue sheet, jacket image, Lyrics, etc.) support.