The Sensor Frames use similar technology as the Sensor Chair, but especially designed to promote ensemble awareness between two players. The electric field sensors are built into two identical picture-frame-like objects, which are hollow and open. The movement of each arm is measured separately (as in conducting) as it approaches or enters the frame area. Each frame is programmed to produce independent sounds, and an interesting polyphony can develop when the two players perform very differently. However, the frames are programmed to look out for similarity of movement between the two players; the more the two players follow each other, the more a special, easily recognizable, chordal sound is produced by the dual instrument. This measurement is very sensitive, and promotes careful listening and watching between the two users.