MuseScore is an absolutely amazing WYSIWYG (read: What You See Is What You Get) music score editor. I use it regularly to arrange and compose many different genres for many different instruments. The layout scheme so flexible, you could call it a music typesetter. It is one of the only DRAG-AND-DROP apps of its kind. (Oh, Finale was such a pain to use…) Imports/exports just about any format you can think of; I've used it back and forth with Finale via MusicXML, and the results are pretty amazing. It's free now, and will be forevermore, so I can rest at ease knowing that I won't have to learn another program ever again.