As an avid iPad music hobbyist, this is really cool. Reminds me a bit of Polychord (http://polychordapp.com/), but Polychord's UI is a bit awkward and the app is incredibly crash-prone. Looks like Fiddlewax has significantly more to offer in regards to melody exploration, which is exactly what I'm looking for. Bought and downloaded.

As if you haven't heard this enough already, throw my vote for MIDI support on the pile. I use iPad synths like Animoog and Sunrizer for writing songs, and being able to combine Fiddlewax's tools with Animoog's sound would be glorious.