Josef Svoboda devised this 10 minute show for the 1958 World Fair (Expo) in Brussels, Belgium with Emil Radok. It was what we would now call a multimedia show or even a video installation because of it's simulaneous showing of multiple images on multiple screens with syncronised sound. The word is a compound word of the Greek poly (more) and the French ecran (screen).
Allegedly 8 automated slide projectors and 7 filmprojectors where used to cover the screens of various sizes, and which were angled in various ways.
It involved no actors thus it cannot be called theater, but it was a remarkable achievement in both technological terms and in terms of live entertainment as it was a completly new format.