Jazz is a musical movement which dominated the 1900s. It is mainly an American form and remains popular to this day. Jazz can be defined as anything from popular music of the twentieth century to the improvised sounds of a dance band. Some prominent forms of Jazz throughout the century have been Ragtime, Blues , Swing , Dixieland Jazz, Bop, and Boogie-Woogie. Since the second half of the 1900s, new forms and techniques of Jazz have come about. These include funky hard bop regression, cool jazz, progressive jazz, and rock and roll. Generally these newer styles have a greater range in harmony, rhythm, and melody, and are less oriented to dance music. They also sometimes borrow techniques and forms from classical music, and vice versa, as modern classical music often contains Jazz elements.