Jazz music that was rooted in the blues, evolved into New Orleans, RAG time, boogie woogie, dixie and swing. Then, in the early decades of the 1940s, jazz entered be bop era. Be bop music was the outlet of the Negro protest in the United States. The atmosphere of World War II made all of society and the musicians frustrated.
Therefore, in a period of 40s, the arcing of new musical forms - one of them was jump band - occurred. Jump band itself was the form of music group that brought the band music of humor and usually contained elements of porn in the lyrics. Then, jump band music branched out into R & B and inspired the form of rock'n'roll that was also a continuation of the development of boogie woogie in the direction of pop or rock music.
In be bop jazz, the limits that were applied in swing jazz were de-emphasized. Be bop jazz was also more expressive and inclined to be more progressive. Thus, since the time, progressive jazz term emerged and jazz music entered into the modern jazz era.
The emergence of rock music and its popularity throughout the world in 1946 were the toughest rival of jazz to keep going and growing. Finally, be bop collapsed and jazz became cool, so came the cool jazz term. Cool jazz lasted from 1949 until 1951. In those days, jazz experienced transition because of pressured by the popularity of rock music.
In modern jazz era or the '60s era, a new form of music - called as soul and funk - arose. Soul music arose from the influence of the gospel church with blues influence. Meanwhile, funk music had 'louder than a pin prick' meaning. It was understood associated with the worldliness because funk was more inclined to commercial.
In addition to these musical forms, there was form of music that was still loyal to the major groove of jazz, eventually called as the hard bop.