Bass Drop Drum N Bass version Free limited time [music app]
Personally, I don't like apps such as this, as you're not really creating music but rather using already created samples and mashing them together without much customization. Another thing to note is that the dev, Ben Frost, has some pretty crappy apps out there; however, a lot of people seemed to enjoy the original dubstep version, one of his better apps. So again, I'm not really into this, but if you just want to mess around with music, you'll like it. Free until the end of this month.