The Musical Synchrotron is a software interface that connects wireless motion sensors to a real-time interactive environment (Pure Data, Max/MSP). In addition to the measurement of movement, the system provides audio playback and visual feedback. The Musical Synchrotron outputs a score with the degree in which synchronization with the presented music is successful. The interface has been used to measure how people move in response to music. The system was used for experiments at public events.