"Improvisation was the blood and bone of jazz, and in the classic, New Orleans jazz it was collective improvisation in which each performer, seemingly going his own melodic way, played in harmony, dissonance, or counterpoint with the improvisations of his colleagues. Quite unlike ragtime, which was written down in many cases by its composers and could be repeated note for note (if not expression for expression) by others, jazz was a performer's not a composer's art."