ELECTRICAL REPRODUCTION OF SOUND
1875	The telephone was invented by Alexander Graham Bell.
1877	Music was transmitted by Bell from Boston to Salem.
1877	The phonograph was invented by Thomas A. Edison, and demonstrated in 1878.
1892	Telephone service was opened from New York to Chicago; in 1911, to Denver; in 1915, to San Francisco.
1915	Experimental radio telephone messages from Arlington heard in Paris.
1918	Radio telephony to airplanes.
1920	Radio broadcasting, Station KDKA; 1922, WEAF
1924	Electrically cut phonograph records.
1926	First commercial sound pictures.
1927	Commercial radio-telephone service, New York to London.
1933	Stereophonic reproduction of music transmitted over telephone wires, Philadelphia to Washington.
1935	Stereophonic reenforcement of music, Hollywood Bowl.
1936	Demonstration of stereophonic reproduction of recorded music to membership of Academy of Motion Picture Arts and Sciences and Society of Motion Picture Engineers.
1940	Stereophonic reproduction of recorded music, New York and Hollywood.