Abstract:

A system for following an improvised jazz solo and inferring the current location in the chord progression is presented. The system will ultimately work in real time in a MIDI environment: It listens to an improvised jazz melody played on a MIDI instrument and joins in the performance with a synthesized rhythm section. It is comprised of two stages: a beat tracker and a performance analyzer. The beat tracker is based on a continuously adapting nonlinear oscillator, which synchronizes to the beats of the improvised solo by continuously adapting its phase and period. It can follow local variations of tempo and produce expectations of next beats. The performance analyzer attempts to infer the current location in the harmonic progression by comparing the notes played in the improvised melody with statistical distributions of notes obtained from improvisations of well-known jazz musicians [T. Jarvinen, Tonal Dynamics and Metrical Structures in Jazz Improvisation (Dept. of Musicology, Univ. of Jyvaskyla, Finland) and trying to find the best match from several possible alternatives. [Work supported by the Academy of Finland.]