Motion Picture Film

The earliest attempts to solve this problem involved motion picture projectors and phonographs rigged with an ingenious system of gears or pulleys that locked them together at the same speed. Later came an entirely different technology based on recording the sound on the film the sound being recorded could be used to control the brightness of a light. The fluctuating light could then be recorded on motion picture film as a separate track called a sound track, which could be played back along with moving pictures.