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 1920s notably with Louis Armstrong, and continued on into the 1940s. 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 alos often known as the big band era.