In 1937’s “Ready Willing and Able” movie features Ruby Keeler and Lee Dixon dancing on the typewriter keys, during the song “Too Marvelous for Words” written by Johnny Mercer.
Here’s a photo taken a few moments earlier or later that Robert Messenger put up on his blog:

Note: Ruby Keeler is a legend to the film industry being a part of the first ever movie with sound with then to be husband Al Jolson in The Jazz Singer.