The early New Orleans "jass" style

A number of regional styles contributed to the early development of jazz. Arguably the single most important was that of the New Orleans, Louisiana area, which was the first to be commonly given the name "jazz" (early on often spelled "jass").

The city of New Orleans and the surrounding area had long been a regional music center. People from many different nations of Africa, Europe, and Latin America contributed to New Orleans' rich musical heritage. In the French and Spanish colonial era, slaves had more freedom of cultural expression than in the English colonies of what would become the United States. In the Protestant colonies African music was looked on as inherently "pagan" and was commonly suppressed, while in Louisiana it was allowed. African musical celebrations held at least as late as the 1830s in New Orleans' "Congo Square" were attended by interested whites as well, and some of their melodies and rhythms found their way into the compositions of white Creole composer Louis Moreau Gottschalk. In addition to the slave population, New Orleans also had North America's largest community of free people of color, some of whom prided themselves on their education and used European instruments to play both European music and their own folk tunes.

By the end of the 19th century, the city was a regional center of Tin Pan Alley popular music and the young style of ragtime, and a distinctive, new musical style began to develop.

According to many New Orleans musicians who remembered the era, the key figures in the development of the new style were flamboyant trumpeter Buddy Bolden and the members of his band. Bolden is remembered as the first to take the blues — hitherto a folk music sung and self-accompanied on string instruments or blues harp (harmonica) — and arrange it for brass instruments. Bolden's band played blues and other tunes, constantly "variating the melody" (improvising) for both dance and brass band settings, creating a sensation in the city and quickly being imitated by many other musicians.

By the early years of the 20th century, travelers visiting New Orleans remarked on the local bands' ability to play ragtime with a "pep" not heard elsewhere.

Characteristics which set the early New Orleans style apart from the ragtime music played elsewhere included freer rhythmic improvisation. Ragtime musicians elsewhere would "rag" a tune by giving a syncopated rhythm and playing a note twice (at half the time value), while the New Orleans style used more intricate rhythmic improvisation often placing notes far from the implied beat (compare, for example, the piano rolls of Jelly Roll Morton with those of Scott Joplin). The New Orleans style players also adopted much of the vocabularity of the blues, including bent and blue notes and instrumental "growls" and smears otherwise not used on European instruments.

Key figures in the early development of the new style were Freddie Keppard, a dark Creole of color who mastered Bolden's style; Joe Oliver, whose style was even more deeply soaked in the blues than Bolden's; and Kid Ory, a trombonist who helped crystallize the style with his band hiring many of the city's best musicians. The new style also spoke to young whites as well, especially the working-class children of immigrants, who took up the style with enthusiasm. Papa Jack Laine led a multi-ethnic band through which passed almost all of two generations of early New Orleans white jazz musicians (and a number of non-whites as well).