The Telharmonium (also: Dynamophon ) is the first electro-mechanical to describe musical instrument. It was built in 1897 by Thaddeus Cahill in Washington, DC developed. The Telharmonium was about 200 tons, was the size of a cathedral organ and was used among other things for the purpose of musical transmission via the telephone. ( So you could listen to music over the phone. ) Despite its enormous size, it was transported for concerts by the United States, where it filled up to 30 boxcars.

Telharmonium the works on the principle of a gear generator ( Each gear generates a sound. The number of teeth of a wheel to determine the pitch in connection with the rotational speed ). The plant was, inter alia, so great, as there were no electronic amplifier and tone generators were thus genuine AC electric generators that had to produce the performance of all the telephone network of speakers ( telephone handset with or without a front mounted hopper ) itself to all listeners to provide them with sufficient sound pressure. The voltages of the generators were mixed together via a complex system of switches and transformers to generate by additive synthesis different timbres that were touch sensitive, a organ console with multiple keyboards.

A total of 3 of these plants have been built, but none of which has been preserved, and no existing sound recordings are known.