On: Easy Listening Acid Trip: An elevator ride through...

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The final sequence in the 1943 (yes, 1943!) movie musical The Gang's All Here ("let's throw a party to encourage people to buy war bonds!") is seriously psychedelic:

https://www.youtube.com/watch?v=VJHfApfdWW0

It's Busby Berkeley, of course, but unlike most of his work, in Technicolor.