MuseScore 1.2

MuseScore is a free cross-platform WYSIWYG music notation program that offers a cost-effective alternative to commercial programs such as Sibelius, Finale and Capella. You can print beautifully engraved sheet music or save it as PDF or MIDI file.

Some highlights:

• WYSIWYG, notes are entered on a "virtual note sheet"
• Unlimited number of staves
• Up to four voices per staff
• Easy and fast note entry with your keyboard, mouse, or MIDI keyboard
• Integrated sequencer and FluidSynth software synthesizer
• Import and export of MusicXML and Standard MIDI Files
• Available for Windows, Mac and Linux
• Translated in 48 languages
• GNU GPL licensed

You can have a look at the detailed features of musescore.