The Tri-Ergon sound-on-film system was patented from 1919 on by German inventors Josef Engl (1893–1942), Hans Vogt (1890–1979), and Joseph Massolle (1889–1957). The name Tri-Ergon was derived from Greek and means "the work of three." (See FilmSoundSweden website under External Links section below.)
In 1926, William Fox of Fox Film Corporation purchased the U. S. rights to the Tri-Ergon patents from Tri-Ergon Aktiengesellschaft (Tri-Ergon AG), Zürich, Switzerland. Fox also purchased sound-on-film patents from Freeman Harrison Owens and Theodore Case and used these inventions to create the new sound-on-film system he dubbed Fox Movietone. One of the first feature films to be released in Fox Movietone was Sunrise (1927) directed by F. W. Murnau. Fox also used the system for the long-running newsreel series Fox Movietone News.
Movietone and other sound-on-film systems were in competition with sound-on-disc systems such as Warner Bros. Vitaphone. However, sound-on-film systems such as Movietone and RCA Photophone soon became the standard, and sound-on-disc fell into disuse.
After Fox lost control of Fox Studios in 1930, he used the Tri-Ergon patents to sue the film industry in order to take a part-ownership in all sound films and in all sound film systems. The Tri-Ergon patents named particular technical features that preceded all other sound-on-film patents, such as a flywheel on the sound drum. Fox at first won his lawsuit and then lost it in an unusual reversal of decision by the U. S. Supreme Court. In Germany, the Tri-Ergon patents were determined to be so strong, for a time all other sound film systems were shut out of that country.
A subsidiary, Tri-Ergon Musik AG of Berlin, made commercial phonograph records for the German, French, Swedish and Danish markets from about 1928 to 1932. Although the product was advertised as "Photo-Electro-Records," it is unknown whether the sound-on-film process was actually used in making them, perhaps for simple cutting of the record.
The Tri-Ergon process involved recording sound onto film using the "variable density" method, used by Movietone and Lee De Forest's Phonofilm, rather than the "variable area" method later used by RCA Photophone.
The Tri-Ergon system used a special form of microphone without mechanical moving parts (Katodophone) for sound pickup and a special electric discharge tube for variable density film recording. For reproduction of sound, the system used an electrostatic loudspeaker.
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