On August 30, 1881, Clement Ader (1841-1926) received a patent in Germany for the first stereophonic system. Two groups of microphones were placed on either side of a stage. These microphones relayed the sound of a play or musical directly to two telephone receivers, which paying subscribers held to their ears. He displayed this invention the same year at the Paris Exposition.

During World War I a similar system was used. What was referred to as "binaural receiving trumpets," were set up to locate enemy aircraft. Two large horns, like those on early phonograph systems, were connected by rubber tubes from their thin ends to the ears of operators. By using these horns, the operator could more readily hear from what direction planes were coming.

In the 1930s, further progress was made in stereophonic systems. The Bell Telephone Laboratories, under the leadership of Harvey Fletcher (1884-1981) and others, including the...