It's narrowly focused on making short 4/4 drum loops--making loops of more than a few bars is hard, complicated melodies are tricky given the resolution of the screen (it's small and by default it jams a couple octaves across it). And the individual sounds try to do a lot for you--they have their own hard-wired effects, in some cases they play complete drum patterns for you, etc.

But you can get started experimenting with piling different sounds on top of each other very quickly, and before you know you'll realize you've been at it for an hour.

In the end I haven't come up with anything I thought was that interesting, but clearly it's possible.