I'm not going to go into the details here - it'll be posted on the Public Radio Tumblr soon - but Zach and I have spent a bit of time reconfiguring our MVP in the past week. The result should be done next week (pending a new 3D printed lid prototype, etc) and will cover all of the functionality of the end product. Right now it's a protoboard, an Arduino Pro Mini, and a couple of (meh) Sparkfun boards.
The shitty thing is finding a potentiometer that will work well. It should be a 10K pot, logarithmic (audio) taper, with a switch. Unless I'm missing some hidden trove, there are about 7 parts in the world that fit those criteria and are stocked in quantities of more than a dozen. And then 5 of those have PC pins, when I think I'll end up needing solder lugs... it's a huge PITA.
Anyway, the project is moving along. More updates soon.