It seems that the new direction of HCI (human computer interaction) is to HIDE computers and merge monitors with interactive surfaces (desks, tables, blackboards, walls and so on).
This is a music generator (it’s better say “wave generator”) that shows great interface mode: objects on the table are scanned and interact with the (hidden) system that feedbacks with lights and sounds.
Here you are the really great movies of reactable! | here the page of the project
The reactable, is a state-of-the-art multi-user electro-acoustic music instrument with a tabletop tangible user interface. Several simultaneous performers share complete control over the instrument by moving physical artefacts on the table surface and constructing different audio topologies in a kind of tangible modular synthesizer or graspable flow-controlled programming language.
(via dr0p.net)
For lazy people a Youtube video here