Jazz originates from the southern states of USA in about 1900. It started when black Americans adapted their traditional work-songs and spirituals into Blues . They then adopted the instruments of the marching brass band, and this music evolved into the form known today as Traditional jazz, New Orleans or Dixieland. One of its main features is improvisation, based on a rigorous harmonic sequence determined by the theme tune of the music. The tunes were usually well known popular tunes of the day, or folk songs or spirituals, and this theme would be clearly stated at the start, usually by the trumpet. But then the players would improvise around this tune, but always maintaining the harmonic sequence.

When Jazz moved North with the migration of black Americans to Chicago, other forms of Jazz evolved, and were taken up and enthusiastically adapted by white musicians.

One such variation is Jazz Swing. Typically, this is music written in 4/4 time, in which dotted quavers followed by semiquavers are played as two thirds then one third of a triplet, giving the swing feel to the music. Lots of popular songs of the 30's, 40's and 50's were orchestrated in the Jazz Swing manner. Frank Sinatra was a famous singer who adopted this style as his own.

Another variation is the Big Band Sound. Here the Traditional Jazz band of trumpet, trombone, tuba (or double bass), and clarinet is greatly enlarged by the doubling or tripling of these instruments, and the addition of tenor and alto saxophones. Glenn Miller is one of the most famous exponents of this style. It was immensely popular in dance halls of the 20's and 30's.

In the late 60's Rock and Roll took over from jazz as the mainstream popular music form. New, more abstract and dissonant forms of Jazz emerged, variously called Cool Jazz, Modern Jazz and Progressive Jazz.   These were never as popular as the earlier forms, and so jazz is now a minority taste for its enthusiastic followers.