In the young days of cinema, one of the first methods for presenting a film with recorded sound was to employ a method of sound on disc. In the mid-1920s, films were occasionally distributed with an accompanying record. The projector for this type of presentation had a record player attached to the base, and the record and film would be synched up by the projectionist. As one might imagine, the synch didn’t always work, sometimes the record would skip or perhaps the operator would put on the wrong record. It wasn’t a perfect system.
In the later 1920s, sound on film, which was a system that had been simmering for a few years, broke through and changed popular cinema forever, effectively killing the silent feature film. This technique of sound on film, still in use today, provides an optical soundtrack on the edge of the film, which means it never goes out of synch (unless there has been a mix-up in the production of the track) as well as avoiding other problems of sound on disc.