Jazz began to "swing" as musicians began to adopt swing eighths, the string bass, high hat cymbals, and a looser, more rhythmic feeling . This change occurred gradually starting in the twenties notably with Louis Armstrong, and continued on into the 40's. A lot of the music that came out of this period was played by bands of ten musicians or more. Because of this the swing era is also often known as the big band era. This definitive history of Swing music documents many of the classic performers of the era including Artie Shaw, Benny Goodman, Cab Calloway, Count Basie, Duke Ellington, Erskine Hawkins, Fletcher Henderson and more.