Recording moving pictures proved hard enough to develop. Adding sound to them took a lot longer — partly for technical reasons, but mostly for a lack of interest on the part of movie studios. Efforts were mad to add sound film as early as 1919 and 1920, by the inventor Lee De Forest, but the audio fidelity suffered, especially compared to a rival method developed by Western Electric and the Warner Brothers move studio.

On this day, April 20, in 1926, Warner Brothers announced a revolutionary new process that would add sound to silent motion pictures. Rather than adding sound directly to film, the studio opted to record it on a disk that would be synced to the action on the screen. Several recent inventions, including two by De Forest, helped WB to perfect that process.

The Warner Brothers picture Don Juan was the first sound film released in theaters. There was no dialogue yet — just music and sound effects — though several features after the film did include dialogue. The first “talkie” picture was The Jazz Singer, which premiered the following year.