Final answer:
Jazz emerged in the early twentieth century, rooted in African American musical traditions like blues and ragtime, and became a popular expression of modernist impulses and the cultural changes during the Harlem Renaissance.
Step-by-step explanation:
Jazz emerged at the beginning of the twentieth century as a result of the increasing demand for music, technological advancements in recording, and a desire to express the cultural dynamics of the time, particularly within the African American community. Jazz, being a uniquely American music form, was born out of the African American communities, with roots in blues and ragtime. It significantly grew in popularity during the 1920s in the period known as the Jazz Age, reflecting a modernist impulse to break away from traditional musical forms and racial barriers.
New York's Harlem neighborhood, in particular, became a cultural hub for jazz, with nightclubs like the Cotton Club hosting legendary musicians such as Duke Ellington and Cab Calloway. The emergence of jazz also coincided with the Harlem Renaissance, a flourishing of African American arts and literature, making it not only a musical revolution but also a social and cultural one.