Ruby Keeler & Lee Dixon dance on a giant typewriter in Ready, Willing & Able (1937)
So jaded by cgi that I didn't think this was impressive at all until I realised it was all an actual size set
It took me a solid few seconds to realize those type bars swinging back and forth at the top are actually peoples legs
...and that the movement of the black-clad-legs striking the paper (ie, typing) corresponds to where the dancers are on the keyboard.