Motion picture film with a “variable area” visual soundtrack on the right edge

For the home consumer, the phonograph (or, as it was often called outside the U.S., the gramophone), was the only widely owned sound recording or reproducing technology through the end of World War II. But in recording studios, particularly in the radio and movie industries, times were changing.
There were numerous attempts to record sound as a visible record rather than a groove, dating from the late 19th century. None was commercially successful until the early 1920s, when several firms introduced sound recording systems that recorded sound onto photographic film. They were all intended to be used with motion pictures, which had emerged as a major money maker in the 1910s. Thomas Edison, Western Electric, and others had developed phonograph-based systems for adding sound to motion pictures, but none worked well due in part to the difficulty of synchronizing the sound to the picture. With the optical systems, the sound was recorded directly onto the same film that held the images, so it was always synchronized. Between about 1906 and 1927, numerous “sound-on-film” optical systems emerged, but they still had technical problems. In fact, many of the early talkies, including the famous film The Jazz Singer of 1927, used the sound-on-disc technology introduced by Western Electric. While perhaps the best of the disc systems, the Western Electric system began to be replaced by improved sound-on-film technologies as early as 1929. Sound-on-film became the standard way to record and reproduce sound in movies through the 1980s, and is still used in a few theaters even today.