Reactable

http://www.youtube.com/watch?v=0h-RhyopUmc

http://mtg.upf.edu/reactable

The reactable, is a multi-user electronic music instrument with a
tabletop tangible user interface. Several simultaneous performers
share complete control over the instrument by moving physical objects
on a luminous 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.

This instrument is being developed by a team of digital luthiers
(Sergi Jordà , Martin Kaltenbrunner, Günter Geiger and Marcos
Alonso), at the Music Technology Group within the Universitat Pompeu
Fabra in Barcelona, Spain.