Jazz is a music genre that originated in the African-American communities of New Orleans in the late 19th and early 20th centuries. Jazz has been recognized as a major form of musical expression in traditional and popular music. Jazz is characterized by swing and blue notes, complex chords, call and response vocals, and improvisation. New Orleans jazz began in the early 1910’s, combining earlier brass-band marches, French quadrilles, ragtime and blues. In the 1930’s, heavily arranged dance-oriented swing bands, Kansas City jazz, a hard-swinging band, bluesy improvisational style and Gypsy jazz were prominent styles. Bebop emerged in the 1940’s, shifting jazz from danceable popular music toward a more challenging style which was played at faster tempos. Cool jazz developed near the end of the 1940’s, introducing calmer, smoother tones, sounds and long, linear melodic lines. The mid 50’s  saw the emergence of hard bop, which introduced influences from rhythm and blues and gospel and blues. Modal jazz developed in the late 1950’s, using mode, or musical scale, as the basis of musical structure and improvisation. Free jazz explored playing without regular meter, beat and formal structures.