From the 1920s to the 1950s, these technologies reached the public in theaters long before anything similar was available from broadcasts or for home use. In fact, many of the early innovations in high fidelity recording and reproduction were created in the context of motion picture production and exhibition, while the phonograph, radio, and television lagged behind. There were experimental linkings of sound and motion pictures from the earliest days of the cinema, and early designers of these systems struggled merely to provide sound at minimally acceptable levels of volume and quality. The nearly worldwide adoption of sound-on-film by the early 1930s corresponded to relatively favorable economic conditions in the motion Picture industry, particularly in the U.S., and this encouraged even more experimentation with new audio techniques.
Some of the most notable achievements of the 1930s were related to stereophonic sound. Long before it was practical to introduce this technology to the public via the phonograph or radio, audiences in some places heard stereo soundtracks accompanying a small number of feature films. A landmark was Fantasia, the animated film by Walt Disney Studios (U.S.), which employed sound recorded on numerous separate optical tracks. These were then mixed down to three channels (left, right and center) of audio for exhibition along with a fourth ‘‘control’’ track, which was not audible but contained information that automatically controlled the volume of each of the three audio tracks. Only two theaters purchased the U.S.$85,000, 54-loudspeaker ‘‘Fantasound’’ system needed to reproduce these films on screen, but a traveling exhibition toured the U.S. when the film opened in 1940.
At the end of World War II, many motion picture producers adopted magnetic recording technology, which was known before the war but rarely used outside Germany. Magnetic recording was substituted for optical recording in the studios primarily because it was much less expensive to use; at a time when television was cutting deeply into theater attendance, cost cutting was imperative. However, that cost saving did not apply to the exhibition of films, and most theaters retained their optical-soundtrack projection equipment through the late 1980s. While studios repeatedly tried to introduce new theater systems using multichannel, high-fidelity sound, most exhibitors resisted. The theater was no longer at the forefront and many innovations in movie sound technology made after the 1950s were preceded by similar innovations in broadcasting or in home high-fidelity systems. However, the experimental technologies of the 1950s are usually cited by film historians as great landmarks. One of the most notable examples was Cinerama, one of several widescreen formats that Hollywood studios believed would bring customers back to the theaters in the 1950s. Besides its remarkably wide screen, Cinerama featured a seven-track magnetic soundtrack, carried on a separate 35 mm film run on a player that was operated in parallel to multiple motion Picture projectors. Like Fantasound before it, Cinerama was so expensive to exhibit that it saw only limited use. Somewhat more successful were systems based on a double-width, 70 mm film on a single projector. All of these used some variation of multichannel sound, and some used magnetic rather than optical soundtracks for theater reproduction. Perhaps the most commercially successful of these was Todd-AO (promoted by film producer Michael Todd and the American Optical Company), which used six audio channels. A series of highly successful innovations was offered by Dolby Laboratories (U.K., later U.S.) beginning in 1965 with the introduction of what came to be known as Dolby A. This was a noisereduction technology used to improve recordings made in the studio before they were released to theaters. Although used initially in the phonograph record industry, the first motion picture soundtrack made using Dolby A was A Clockwork Orange. Released in 1971, the movie was typical of the Dolby releases of the day in that it was originally recorded on multitrack magnetic recorders, mixed using Dolby noise reduction, but released in ordinary monophonic form, usually with an optical soundtrack. However, the next year Dolby introduced an improved optical soundtrack technology and the short film A Quiet Revolution was released to demonstrate to theater chain owners the value of using Dolby noise reduction equipment in the exhibition of these films. While this technology did not succeed, some theaters did begin to improve their audio equipment. Sensurround, a multichannel system for theaters, was introduced as a sort of novelty with the film Earthquake in 1974. An optically recorded, inaudible control track triggered the reproduction of very low-frequency sounds, which were used to add emphasis to the soundtrack at key points (such as the rumbling of an earthquake). Sensurroundlike systems would eventually evolve into the current ‘‘Surround Sound,’’ but meanwhile the Dolby Laboratories once again introduced a new multitrack system. This one, called Dolby Stereo, electronically combined four soundtracks onto just two tracks for the final release print. The four tracks included left, right, and center channels plus a ‘‘surround’’ channel for special effects. Dolby Stereo could be reproduced by adding relatively inexpensive accessories to existing projectors. The first release in Dolby Stereo was A Star is Born in 1976. Following the advent of Dolby Stereo it became more common to advertise a film’s sound technology along with its cast. This helped generate a popular interest in film sound, and along with the consolidation of exhibition and production companies, the rate of adoption of new theater technologies began to accelerate.
Digital recording techniques were tried by filmmakers from the early 1980s, although they were not in widespread use until the 1990s. An early optical digital playback system introduced in 1990 by the Eastman Kodak Company (U.S.) was not as successful as Dolby Digital, introduced in 1992. In this new system, a digitized version of the soundtrack was placed in the tiny spaces between the sprocket holes on the exhibition copy of the film, thus leaving room for a conventional analog soundtrack at the edge to be used as a backup or in theaters that had only the standard projectors. Under various names, the software algorithms developed for Dolby Digital have also been adapted for other formats, such as home theater and DVD discs. With the introduction of digital recording and playback systems, motion Picture producers and movie theaters are once again acting as the channels for the introduction of new audio technologies to the public.