What is "reactable"

The Reactable is an electronic musical instrument with a tabletop Tangible User Interface that has been developed within the Music Technology Group at the Universitat Pompeu Fabra in Barcelona, Spain by Sergi Jordà, Marcos Alonso, Martin Kaltenbrunner and Günter Geiger.

In late 2010, a mobile version of the Reactable was released for iOS.