Cyril Stoller shares this project, for a variety of multitouch devices (Mac / Windows / Linux / Android, screens and projection) through the also-free-and-open-source Kivy framework. It’s inspired by the brilliant Haken Continuum fingerboard, but whereas that more tactile controller is hard to get, this runs cheaply all over the place. (It could also be a way to practice and save up for a Haken, it occurs to me.)
Thanks to Graham Comerford for the tip. I wonder what other ideas might apply to playing multitouch as an instrument.
More discussion on the excellent NUI forum – a great spot for alternative and gestural interaction chatter and resources: