Jazz is a genre of music that originated in African-American communities during the late 19th and early 20th century. Jazz emerged in many parts of the United States of independent popular musical styles; linked by the common bonds of European American and African-American musical parentage with a performance orientation. Jazz spans a range of music from ragtime to the present day—a period of over 100 years—and has proved to be very difficult to define. Jazz makes heavy use of improvisation, polyrhythms, syncopation, and the swung note, as well as aspects of European harmony, American popular music, the brass band tradition, and African musical elements such as blue notes and ragtime. A musical group that plays jazz is called a jazz band.As jazz spread around the world, it drew on different national, regional, and local musical cultures, giving rise to many distinctive styles. New Orleans jazz began in the early 1910s, and it combined earlier brass band marches, French quadrilles, biguine, ragtime, and blues with collective, polyphonic improvisation. Heavily arranged dance-oriented swing big bands, Kansas City jazz, a hard-swinging, bluesy, improvisational style and Gypsy jazz, a style that emphasized Musette waltzes, were important styles in the 1930s. Bebop emerged in the 1940s; it shifted jazz from danceable popular music towards a more challenging "musician's music" which was played at faster tempos and used more chord-based improvisation. Cool jazz developed in the end of the 1940s, introducing calmer, smoother sounds and long, linear melodic lines. Free jazz from the 1950s explored playing without regular meter, beat and formal structures.Hard bop emerged in the mid-1950s, introducing influences from rhythm and blues, gospel music, and blues, especially in the saxophone and piano playing. Modal jazz, which developed in the late 1950s, used the mode, or musical scale, as the basis of musical structure and improvisation. Jazz-rock fusion developed in the late 1960s and early 1970s by combining jazz improvisation with rock rhythms, electric instruments and rock's highly amplified stage sound. In the early 1980s, a commercial form of jazz fusion called "smooth jazz" became successful and garnered significant radio airplay. Other jazz styles include Afro-Cuban jazz, West Coast jazz, ska jazz, Indo jazz, avant-garde jazz, soul jazz, chamber jazz, Latin jazz, jazz funk, loft jazz, punk jazz, acid jazz, ethno jazz, jazz rap, M-Base and nu jazz.Louis Armstrong, one of the most famous musicians in jazz, made this observation on the history of the music: "At one time they were calling it levee camp music, then in my day it was ragtime. When I got up North I commenced to hear about jazz, Chicago style, Dixieland, swing. All refinements of what we played in New Orleans... There ain't nothing new." In a 1988 interview, jazz musician J. J. Johnson said: "Jazz is restless. It won't stay put and it never will."