The Reactable

From the website of the creators of the reactable (from the Music Group at Universitat Pompeu Fabra in Barcelona, Spain)

"The reactable is a collaborative electronic music instrument with a tabletop tangible multi-touch interface. Several simultaneous performers share complete control over the instrument by moving and rotating physical objects on a luminous round table surface. By moving and relating these objects, representing components of a classic modular synthesizer, users can create complex and dynamic sonic topologies, with generators, filters and modulators, in a kind of tangible modular synthesizer or graspable flow-controlled programming language. "

(Thanks Xaviera!)