Why is it that in western movies and documentaries the pianos are sometimes playing by themselves?

Question

Why is it that in western movies and documentaries the pianos are sometimes playing by themselves?

In: Technology

Answer 1

Self-playing pianos that used pressurized air or electric actuators to operate the machine like a big music box were a popular novelty until the market crash in 1929.

The song would be “programmed” onto a roller or perforated sheet and the piano would play it by itself, provided you connected power or pressurized air.

Answer 2

Because those were ‘player pianos’ that played by themselves.

They often had a programming in the shape of punch hole roles that told it which notes to play.