If you thought you had to pay an arm and a leg for a top-notch musical notation editor, think again. MuseScore is powerful, versatile, and free. It may not offer the bells and whistles provided by some of the paid competition, but the core functionality is there: WYSIWYG creation and editing, support for unlimited staves, unlimited score length, a plug-in architecture, and excellent-looking notation. See all Software reviews.
The more I played with MuseScore, the more impressed I became. There's fine control over the size and spacing for nearly every object: clef, stave, accidental, performance mark, etc. that most users will need. It has MIDI input, Music XML import and export, its own internal sounds, and support for ASI0 (a low latency audio standard) and JACK MIDI (a free patch bay that works between MIDI programs), though not the more popular Rewire (another patch bay/signal router). See all software downloads.
If you're used to Sibelius or Finale, you'll probably feel right at home with MuseScore. I'd prefer a simple left-click to do something other than just drag the page around, but that's me. One area where the program hits the nail on the head is allowing you to drag note modifiers and performance markings directly to the notes they will operate on. Brilliant.
Also brilliant is allowing users to redefine the keyboard shortcuts, though the process could be streamlined a bit. MuseScore is as challenged in the area of mouse editing as the rest of the notation industry, which has never seemed to fully grasp the drag-and-drop concept. But all in all, it's as easy for entering symbols and editing as the competition is.
Most MuseScore features work flawlessly, but I did find a couple of oddities. The program imported a piano MIDI file onto a single treble stave, rather than the usual treble and bass staves. There's a split staff function, but it would be nice to automate the process. Also, playback volume for the internal synthesizer was very low. Other than that, the program seemed stable as a rock.
MuseScore is built on the cross-platform QT library and is also available for both Linux and the Mac. I highly recommend taking it for a test spin if you're in the market for your first notation program, or to see just how powerful free can be. Don't forget to check out the plug-in library which may offer any functionality that you find missing. See all Software reviews.