“ReacTable” allows several simultaneous performers to share complete control over the instrument by moving and rotating physical objects on its luminous round table surface. This translucent multi-touch tabletop conceals underneath itself a wide-angled camera, which continuously analyzes the surface, tracking the players’ fingertips, as well as the nature, position and orientation of the various objects that are distributed on the table. The objects themselves represent the components of a classic modular synthesizer, while their relative distances and orientation define the topological structure and parameters of the sound synthesizer. A projector, also located just underneath the table, draws dynamic animations on the tabletop, thus providing a visual feedback of the state, the activity and the main characteristics of the sounds produced by the audio synthesizer. The instrument enables users to create complex and dynamic sonic topologies, with generators, filters and modulators – all by simply moving and relating physical objects placed on top of the “ReacTable”.