Jazz music is a product of the Atlantic slave trade, which brought Africans to the United States throughout the 18th and 19th centuries. Among other cultural traditions practiced by African slaves in America was a form of African music that was very different from the established European model. Gradually, slaves (and, eventually, their descendants) began to blend African scales and styles with European instruments. This led to the development of ragtime and blues music before culminating in another new genre of music that was dubbed jazz.
The music that would eventually be called jazz developed in and around the melting pot of New Orleans in the early-20th century. This music was characterized by strong rhythms and a lack of harmony, the use of blues notes, and a call and response structure, all of which were the legacy of African music. To this basic structure early jazz musicians added European instruments like the piano, as well as brass instruments such as the trumpet. Some notable musicians from this period include Scott Joplin and Jelly Roll Morton.
In the 1920s, growing industrial production in northern American cities lured many people from the south who gave up their agricultural lifestyle and became urban dwellers in places like Chicago. Jazz music, still in its infancy, went with them. The 1920s became known as the Jazz Age with the popularity of jazz clubs and the emergence of celebrity performers such as Louis Armstrong, George Gershwin and Duke Ellington. Jazz became associated with big bands that resembled orchestras, though solos remained an important part of most jazz compositions.
It was perhaps inevitable that jazz music would travel outside the United States to continue its progression as a popular form. This began to happen as early as the 1930s, when jazz became a favorite musical style in France. In Europe, new musical traditions were fused with jazz. Among the new forms created was so-called gypsy jazz, which was pioneered by Django Reinhardt and became one of the first types of jazz not native to America.
Beginning around World War II, jazz music began to branch into a series of distinct subgenres, each of which borrowed the basic form of jazz while adding something new. Bebop emerged in the 1940s as a more complex form of jazz that was more suitable for the concert hall than the dance hall. Cool jazz, epitomized by Miles Davis, brought new musical theories to jazz and added the important element of improvisation. Free jazz was an effort to break down the boundaries imposed by the various jazz forms and give musicians greater freedom to explore new techniques and composition structures. Jazz continues to evolve today, incorporating world music and pop music.