Pittsburgh Gazette Times, December 28, 1919, First section, page 8: (Full article at Google newspapers.)
PITTSBURGHER GIVES CONCERT BY WIRELESS; 200 HEAR SELECTIONS
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Vocal and Instrumental Music Through Means Of Telephone Attachment and Phonograph.
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There was music in the air last night.
Persons walking along the city streets were probably unaware that vocal and instrumental solos by noted artists could be heard for many miles. Yet 200 wireless operators throughout Western Pennsylvania were eagerly awaiting the first strains to come over the wireless telephone equipment.
The third of a series of "Conrad Open Air Concerts" was given by wireless from his laboratory at Penn avenue and Peebles street.
Shortly before 9 o'clock J. B. Coleman of 328 Locust street, Edgewood, and Mr. Conrad's sons, Francis and Crawford Conrad, began preparations in the laboratory for the open air musical. A few taps on the wireless telegraph key by Mr. Coleman announced the concert was about to start.
A record was put on a phonograph and the telephone was placed at the mouth of the phonograph. The machine was started and the concert was on.
The audience, scattered for many miles, was treated to almost everything musical with the exception of piano solos, for piano notes do not carry well through the air. There was band music, vocal, violin and other instrumental solos. The concert continued until 10 o'clock when the music was stopped so as to prevent any confusion in the air while the government stations sent out messages, such as weather news and the correct time.
There was no applause to the concert last night, but Mr. Conrad said many members of his audience would send approval by the telephone and wireless telegraph today.