A year before The Jazz Singer
premiered, audiences at a theater in New York watched in awe as images of a violinist, a vocalist, and an actor talked and played music from the movie screen. Engineers achieved this effect using the vitaphone, a new invention hailed as the long-awaited breakthrough in talking movies. As the diagram pictured left shows, the machine worked by recording sound on a master disk, while two electrically interlocked motors synchronized images with the sound. While filming, the camera would record images while a microphone on the ceiling would record sound and convert it to electrical impulses, which traveled through a vacuum tube to an amplifier. The impulses would then form groove formations on the sound disk. In the theater, an image projector and the sound disk operated from different ends of a motor. While the images played, a needle would translate the disk's impressions into electrical surges, thus creating amplified sound.
As you can see in the artist's diagram, one horn-shaped projector would transmit sounds recorded on the film, like the dialogue, while two other horns would transmit the orchestra accompaniment. Not long afterward, The Jazz Singer would use this very technology to become the first feature-length film with synchronized dialogue.
Read the full story in "How Shadows Talk from the Screen"