Jazz has roots in the combination of Western and African music

Jazz has roots in the combination of Western and African music traditions, including spirituals, blues and ragtime, stemming ultimately from West Africa, western Sahel, and New England's religious hymns and hillbilly music, as well as in European military band music. After originating in African American communities near the beginning of the 20th century, jazz gained international popularity by the 1920s. Since then, jazz has had a pervasive influence on other musical styles worldwide. Even today, various jazz styles continue to evolve.

The word jazz itself is rooted in American slang, probably of sexual origin, although various alternative derivations have been suggested. According to University of Southern California film professor Todd Boyd, the term was originally slang for sexual intercourse as its earliest musicians found employment in New Orleans brothel parlors.

At the root of jazz is the blues, the folk music of former enslaved Africans in the U.S. South and their descendants, heavily influenced by West African cultural and musical traditions, that evolved as black musicians migrated to the cities. According to jazz musician Wynton Marsalis:

Jazz is something Negroes invented, and it said the most profound things -- not only about us and the way we look at things, but about what modern democratic life is really about. It is the nobility of the race put into sound ... jazz has all the elements, from the spare and penetrating to the complex and enveloping. It is the hardest music to play that I know of, and it is the highest rendition of individual emotion in the history of Western music.[1]

Early jazz influences found their first mainstream expression in the marching band and dance band music of the day, which was the standard form of popular concert music at the turn of century. The instruments of these groups became the basic instruments of jazz: brass, reeds, and drums, and are voiced in the Western 12-tone scale.

Black musicians frequently used the melody, structure, and beat of marches as points of departure; but says "North by South, from Charleston to Harlem," a project of the National Endowment for the Humanities: "...a black musical spirit (involving rhythm and melody) was bursting out of the confines of European musical tradition, even though the performers were using European styled instruments.

Many black musicians also made a living playing in small bands hired to lead funeral processions in the New Orleans African-American tradition. These Africanized bands played a seminal role in the articulation and dissemination of early jazz, traveling throughout black communities in the Deep South and to northern cities.

For all its genius, early jazz, with its humble folk roots, was the product of primarily self-taught musicians. But an impressive postbellum network of black-established and -operated institutions, schools, and civic societies in both the North and the South, plus widening mainstream opportunities for education, produced ever-increasing numbers of young, formally trained African-American musicians, some of them schooled in classical European musical forms. Lorenzo Tio and Scott Joplin were among this new wave of musically literate jazz artists. Joplin, the son of a former slave and a free-born woman of color, was largely self-taught until age 11, when he received lessons in the fundamentals of music theory from a classically trained German immigrant in Texarkana, Texas.

Also contributing to this trend was a tightening of Jim Crow laws in Louisiana in the 1890s, which caused the expulsion from integrated bands of numbers of talented, formally trained African-American musicians. The ability of these musically literate, black jazzmen to transpose and then read what was in great part an improvisational art form became an invaluable element in the preservation and dissemination of musical innovations that took on added importance in the approaching big-band era.