In 1930s Britain, the Post Office started up a Savings Bank (this still exists, its now called National Savings and Investment) - this somewhat psychedelic film made by Len Lye was commissioned to advertise it.
Len would paint directly onto the 35mm film stock, as soundtracks were optical they could easily be synchronised as looking at them with a magnifier would show the same images as the waves on a modern DAW or Audacity type software..
