The feedback guitar enables the acoustics of the guitar strings to be reprogrammed using feedback control. New sounds and new interactions are possible.

  At the Acoustical Society of America meeting in Louisville, I presented about how the feedback control works even though it has six sensors. As shown in the Figure below (with N=6), each string responds individually to the same force from the controller K(jw). If the outputs of the string sensors are summed, then it can be used as a feedback control system.


Incredibly, the bullet points below explain how the phase angle of the instrument is limited to the positive real range, which means that the feedback control can be realized using physical models.