The first jazz bands contained a "rhythm section" consisting of a string bass, drums, and a guitar or banjo, and a "melodic section" with one or two cornets, a trombone, a clarinet, and sometimes even a violin. Years later, jazz was taken over by large orchestras; a "society jazz band" contained fifteen or more musicians. Today, there is a renewed interest in the "big band" era, even though the music has very little to do with real jazz.

           True jazz is characterized by certain essential features. The first is a tendency to stress the weak beats of the bar (2nd and 4th) in contrast to traditional music which stressed the first and third beats. The second feature is syncopation through an extensive repetition of short and strongly rhythmic phrases or "riffs". The third feature of jazz is swing  (regular but subtle pulsation which animates 4/4 time). The swing must be present in every good jazz performance.