Music notation and composition software

MuseScore is a free and open source music notation software with a
WYSIWYG design — notes are entered on a virtual staff.
Features include unlimited staves, up to four voices per staff,
fast note entry with mouse, keyboard or MIDI, MusicXML and MIDI import/export,
integrated sequencer with FluidSynth software synthesizer for playback,
print or PDF export, and translations in 26 languages.