Since the early days of radio broadcasting, the disc jockey or DJ has been an essential part of radio, not just playing records but serving as an intermediary between the listening audience and the stars of popular music. Disc jockeys enjoyed the most influence on their listeners in the 1950s and 1960s, when they introduced new music to Americans and made rock and roll the dominant force in youth culture.

In the first two decades of radio in the United States, the person who introduced records and made station announcements was usually a technician who worked the broadcast equipment. It was a policy of the large radio networks to avoid recorded sound as much as possible and rely on live programming. Thus there was little call for disc jockeys in the 1920s and 1930s. The radio networks were forced to drop their opposition to canned music...