Real-Time Performance Interaction with a Computer-Controlled Acoustic Piano

Abstract

Interactive computer control of synthesized sounds has been practiced for a quarter century. Examples of direct control of acoustic instruments have also been demonstrated in compositions presented over the last decade. In this article, we describe what we believe to be the first instance of real-time interaction between performer and computer that is entirely within the realm of acoustic piano sounds. A pianist performs the score on an acoustic piano, controlling a second, computer-generated part solely through his or her performance. This second part is played by the computer on the same piano-a genuine duet for a single pianist. The pianist plays on the Yamaha Disklavier, which looks like an ordinary piano, but is specially equipped with sensors and motors. The sensors send output electrical signals that provide information on the movements of the keys and the pedals. The motors can be triggered by external signals that set the keys and the pedals into motion. Signals in both directions are coded according to the MIDI protocol. To implement live interaction, we have inserted a computer between the MIDI signals coming out of the piano and the MIDI signals going back into the piano. The computer processes the MIDI signals it receives from the piano, and sends back MIDI signals that cause the piano to play a second part. This computer response depends both upon the specific notes played by the pianist and the way the notes are played. The relation between the pianist's part and the computer's part is specified in the computer program. We first review earlier interactive computer music systems. Then we explain the initial difficulties we encountered in the present work, and the technical implementation of Duet for One Pianist (1989), a piece composed by one of us (Jean-Claude Risset) and implemented by both authors. We describe several kinds of interactive relations between the pianist and his virtual partner. Sound examples are included on the Computer Music Journal Volume 20 CD.