Abstract: The system involves irradiating a performance zone with microwave energy of a frequency of the order of 10.69 GHz and placing a doppler effect sensor where it can pick up reflections from a moving performer and produce signals indicative of movement of any part of the performer. At the same time, other sensors arranged in a spatial matrix covering the performance zone produce signals indicative of instantaneous position. The outputs of all sensors are processed by a master control unit which in turn governs the output of a visual or audio channel, or both. The spatial matrix can be in the form of intersecting infrared laser beams or pressure or proximity sensors in the floor of the performance zone.