Augmenting the Acoustic Piano with Electromagnetic String Actuation and Continuous Key Position Sensing

This paper presents the magnetic resonator piano, an augmented instrument enhancing the capabilities of the acoustic grand piano. Electromagnetic actuators induce the strings to vibration, allowing each note to be continuously controlled in amplitude, frequency, and timbre without external loudspeakers. Feedback from a single pickup on the piano soundboard allows the actuator waveforms to remain locked in phase with the natural motion of each string. We also present an augmented piano keyboard which reports the continuous position of every key. Time and spatial resolution are sufficient to capture detailed data about key press, release, pretouch, aftertouch, and other extended gestures. The system, which is designed with cost and setup constraints in mind, seeks to give pianists continuous control over the musical sound of their instrument. The instrument has been used in concert performances, with the electronically-actuated sounds blending with acoustic instruments naturally and without amplification.