Improvizing with Genetic Algorithms: GenJam

Imagine you are walking down the street past a coffeehouse that features live jazz. From inside the coffeehouse you hear a jazz quartet begin to play a tune. As you pause outside to listen, it sounds like a tenor sax player backed up by a standard jazz trio of piano, bass and drums. You recognize the tune as John Coltrane’s

Giant Steps

as the tenor player plays the song’s original melody in the first chorus of the tune. Once this ‘head’ chorus is complete, everyone continues playing in the second chorus, but the tenor player plays a melody that is decidedly not the original melody of the song, switching from the half note rhythm of the original melody to a more active eighth-note-based rhythm. The piano, bass, and drums seem to be playing things that are similar to what they played on the first chorus, except that the bass player is playing a note on every beat instead of roughly every other beat, and the drummer is more active and assertive. This continues for four more improvized choruses, at which point the tenor player begins playing the original melody of the tune again. After this reprise of the tune’s head, there is a brief coda and the tune ends.