Lee de Forest also used the arc-transmitter to conduct some of the earliest experimental entertainment radio broadcasts - see birth of public radio broadcasting.
Eugenia Farrar sang I Love You Truly in an unpublicized test from his laboratory in 1907, and in 1908, on Lee de Forest's Paris honeymoon, musical selections were broadcast from the Eiffel Tower as a part of demonstrations of the arc-transmitter - wikipedia 
However Reginald Fessenden reported that as early as late 1906, he also made the first radio broadcast of entertainment and music, although a lack of verifiable details has led to some doubts about this claim (which he first made in 1932) - see first entertainment radio broadcast.
# Public speech by radio
In early 1909, in what may have been the First public speech by radio, de Forest's mother-in-law, Harriot Eaton Stanton Blatch, made a broadcast supporting women's suffrage.
# Opera
More ambitious demonstrations followed. A series of tests in conjunction with the Metropolitan Opera House in New York City were conducted to determine whether it was practical to broadcast opera performances live from the stage. Tosca was performed on January 12, 1910, and the next day's test included Italian tenor Enrico Caruso.
February 24, 1910 radio broadcast by Mme. Mariette Mazarin of the Manhattan Opera Company. From page 333 of the August 1922 issue of ''Radio Broadcast''.
- wikimedia.org
On February 24, the Manhattan Opera Company's Mme. Mariette Mazarin sang "La Habanera" from ''Carmen'' over a transmitter located in De Forest's lab.