This is the simplest and best thing I’ve ever seen for creating music fast. It’s massively usable. You can literally get into it by clicking a few keys – admittedly you’ll be making derivative euro-dance. But it’ll sound totally competent no matter how incompetent you secretly are. Go there and have a play, it’s blooming awesome: http://www.tony-b.org/. Really. Do. It’s great.
Even thought the music is really cheesy playing with this put a real smile on my face!