It's basically an iPad sequencer with the UI of a drawing app. You're given a canvas that can be panned and zoomed like any scroll view, with a grid indicating time on the horizontal axis and pitch on the vertical axis. You draw notes with your finger, and although you can snap to the grid like in most sequencers, you can also choose to start your notes at any point and bend them to any pitch. This makes it simple to experiment with things like guitar solos and complex rhythms. Usability was my primary goal through and through: I wanted almost anyone to be able to pick up my app and start making music in an instant. In a way, I see it as a kind of modern take on sheet music!
More about the design here: http://beta-blog.archagon.net/2016/02/05/composers-sketchpad...
The app is out but I still have a ton of features I want to add, including iPhone support.