MuseScore is a free cross platform WYSIWYG music notation
program, licenced under GNU GPL. Features:
* WYSIWYG, notes are entered on a "virtual note sheet"
* unlimited number of staves
* up to four voices/staff
* easy and fast note entry with mouse, keyboard or midi
* integrated sequencer and FluidSynth software synthesizer
* import and export of MusicXml and standard midifiles (SMF)
* platform independent code for Linux, Windows and Mac
jack-audio-connection-kit and portaudio are optional dependencies.