n.
Jazz played with a steady beat using the harmonic structure of popular songs and the blues as the basis for improvisations and arrangements.
The popular music of the U.S. from about 1930 to 1945 (years sometimes called the swing era), swing is characterized by syncopated rhythmic momentum with equal stress accorded to the four beats of a measure. Larger jazz bands required some arranged material, and Fletcher Henderson , Duke Ellington , and Count Basie were the primary innovators of big-band swing. In smaller ensembles, improvised instrumental solos generally follow a rendering of the melody.