ELI5, movies were made with photos that played very quickly, but how was sound added to that when it did?

Question

ELI5, movies were made with photos that played very quickly, but how was sound added to that when it did?

In: 3

Answer 1

The sound and picture used to be separate. At first it was a live group or pianist at the corner of the screen playing piano. Phonograph or record players could be used.

A magnetic strip on the film similar to tape was experimented with until the sound was encoded optically onto the film media.

[16mm film with optical audio track.](https://en.m.wikipedia.org/wiki/16_mm_film)