Jazz developed in the early twentieth century in New Orleans, Louisiana. The town was a seething ethnic melting pot: Before French domination, then Spanish, became part of the United States with the "Louisiana Purchase" of 1803. The Jazz immediately establishes itself as a synthesis of many musical cultures, European (military band music, songs from the church, opera) and African (percussion, rhythm). The main elements of jazz are two: rhythm and improvisation. From the technical point of view, the modern jazz is characterized by the extensive use of improvisation, of blue notes, chord progressions of polyrhythms and unusual when compared with those used in classical music. In particular, the rhythmic pulse of jazz, elastic and sometimes punctuated unequally, called Swing, has been important in nearly all forms of this music.
The swing is a kind of music jazz, born in the twenties and evolved to become a genre defined in 1935 in the United States. The swing is distinguished by a characteristic movement of the rhythm section and a type of execution of the notes at a rate "jumpy" (or "swinging", just swing in English) The swing has developed simultaneously in two completely different environments: New York and Kansas City.