Spectral Harp - sound toy for iOS

I recently used openFrameworks to make my second iOS audio app. This one is a simple instrument where you strum strings to vibrate parts of the audio spectrum and wind up with cool alien and robot sounds. It looks like this:

And here’s what it sounds like:

https://soundcloud.com/ddf/spectral-harp-demo

I’d be curious to know what people think about the interface, like suggestions for making it look nicer or maybe a better layout. I’m hoping to be able to add MIDI control and inter-app audio at some point.

Here’s the iTunes preview link: https://itunes.apple.com/us/app/spectral-harp/id527484081?mt=8

I’d be very interested to see a video showing the interaction. It would also help people give feedback. The audio is interesting, the variability has a good progression through different timbres/gestures (no too arbitrary).