This detailed technical film explains through animation, diagrams, and footage of recording equipment how sound is recorded for motion picture films. There are many interesting scenes of how this engaging process works, including shots of the narrator of the film shown actually recording the soundtrack in real time. As the film will explain in more detail, photographic light valves imprint the film to make variable density soundtracks. The film includes shots of vintage projectors and footage of the actual sound variations that allows an audience to “see” a soundtrack. Grand footage of old microphones and music recording equipment highlight this intriguing classic educational video.