Edison Records
Thomas A. Edison invented the phonograph, the first device for recording and playing back sound, in 1877. After patenting the invention and benefiting from the publicity and acclaim it received, Edison and his laboratory turned their attention to the commercial development of electric lighting, playing no further role in the development of the phonograph for nearly a decade. Edison's original phonograph recorded on sheets of tinfoil and was little more than a crude curiosity, although one that fascinated much of the public. These earliest phonographs were sold mainly to entrepreneurs who made a living out of traveling around the country giving "educational" lectures in hired halls or otherwise demonstrating the device to audiences for a fee. The tinfoil phonograph was not fit for any real practical use and public interest soon waned.
Theodore Case
From 1921 to 1924, Case provided Lee De Forest, inventor of the audion tube, many inventions from his lab that made DeForest's Phonofilm sound-on-film process workable, though DeForest had been granted general patents in 1919. To develop a light for exposing a soundtrack to film, the Case Lab converted an old silent-film projector into a recording device. With it, the AEO light was created, which was mass-produced for use in all Movietone News cameras from 1928 to 1939, and in recording sound in all Fox feature films from 1928-1931. Movietone News used a single-system to record the sound and image simultaneously in a camera, while feature film production moved to a system that recorded sound on a separate machine that was essentially a sound camera with the lenses and picture shutter missing. It was an optical tape recorder that used film rather than tape and was mechanically interlocked with the picture camera.