Real-Time Computer Accompaniment of Keyboard Performances

Abstract

We have extended the capabilities of real-time computer accompaniment by developing fast inethods for matching polyphonic performances against scores. and we have improved the musicality of the accompaniment through the use of a number of accompaniment heuristics and techniques. A set of algorithms has been designed to handle streams of partially ordered events typified by the key-down events of a keyboard performance. The new algorithms can be viewed as points in a space of alternative designs, where the dimensions are (1) the choice of function that evaluates the quality of a perlbnance/score association, (2) the method of determining when to trust tile current guess as to score location, and (3) the method of dealing with compound, unordered events in the score. Two or more alternatives along each of these dimensions are described. Substantial progress has been made in the area of controlling the rate of passage of musical time to achieve a musical accompaniment as the soloist speeds up, slows down, and skips around in the score. Several heuristics tbr musical accompaniment are presented. Accompaniment systems based on this work are operational, and demonstrate the viability of these techniques, This research was sponsored by the Defense Advanced Reseamh .Projects Agency (DOD), ARPA Order No. 3597, monitorcd by the Air Force Avionics Laboratory Under Contract F33615-81-K-1539.