In its early days, radio was a medium for live entertainment. The dramas, comedies, and music were all performed in the studio at the time of broadcast. In the event that live entertainment was unavailable, an announcer would apologetically advise the listening audience: "This next song is from a phonographic record."
In 1934, Al Jarvis, an employee of at KFWB in Los Angeles, came up with an idea he called "Make Believe Ballroom."
He'd play Big Band records, use audience applause from a sound effects record, and talk in-between songs like a live emcee would. The show was a local hit—and an assistant at the radio station, Martin Block, was taking notes.
Block eventually moved to New York and was hired by WNEW. At the time, Bruno Hauptmann—who was accused of kidnapping and murdering Charles Lindbergh's 20-month-old son—was on trial, and while the station was awaiting news updates, Block played records and re-created the Make Believe Ballroom. His program became a huge hit and, thanks to WNEW's large audience and broadcast range, Block gained fame as America's first Disc Jockey, relegating Al Jarvis to footnote status in radio history books.