This review covers Lee DeForest's activities in New York City, in 1915 to 1916, featuring his experimental "Highbridge" station, 2XG. Contrary to DeForest's assertion that this was the first time promotional announcements had been made in exchange for a company supplying phonograph records, Charles Herrold in San Jose, California had already done the same thing, dating back to at least 1912.
Father of Radio, Lee DeForest, 1950, pages 337-338:

    The top of our High Bridge tower, 125 feet above the factory roof, was yet far below the level of the High Bridge and Washington Bridge, and of the stone cliff on the west side of the Harlem River opposite us. A less desirable site for a transmitting station could scarcely be imagined. However an antenna was now rigged and systematic tests of our transmitter panels and oscillator tubes were undertaken.
    Logwood and I had a number of skilled radio-fan friends in Manhattan and the Bronx, and soon our phone was kept busy with reports from these listeners and others as far afield as Bridgeport, Connecticut, and down New Jersey way.
    One hundred and twenty-five watts output from one tube was our limit as yet. I was after ten times that amount. We now began installing the first "Radio Concert" transmitter at the Columbia Gramophone Building on 38th Street as probably giving us greater ranges than from High Bridge; and with a very sound business idea, thereby to greatly increase our sale of Audions and listening equipment. And Columbia was interested, as a very cheap sponsor, because I was to play each day a goodly number of their new records, announcing the title and "Columbia Gramophone Company" with each playing. Thus I became the world's first "disk jockey." That was then the limit of my radio advertising for this early sire of "CBS."
    This was unquestionably the first "sponsored" radio program service. It aroused a deal of interest on the part of radio fans, not merely telegraph-code hams, and our sales of radio receivers, Audions, and crystal sets, began to pick up most gratifyingly.
    Broadcasting coverage from the 38th Street Columbia Building proving no greater, I moved the transmitter back to the High Bridge tower and resumed our testing, taking with me the Columbia phonograph and a goodly supply of records, with which I continued generously to regale all radio listeners. I distinctly remember how I then began to extol through the microphone the merits of our various radio wares; rather shamefacedly it is true, because I still cherished the earlier, quixotic idea that nought but good music and good entertainment or educational matter should go out over the radio. And when shortly thereafter the Western Electric Company opened up a radiotelephone transmitter for testing purposes on their West Street building, we heard them announce that "they had no superior quality variable condensers for sale." I felt the implied rebuke so keenly that thereafter all advertising matter was taboo from any radio station which I controlled.