Busby Berkeley
A director & musical choreographer known for his elaborate musical production numbers, where he organized dancers into large geometric and kaleidoscopic patterns.
Peak popularity as choreographer during the Great Depression, but transitioned to purely directing when the big musical numbers he was known for fell out of fashion.
In the cinematic realm, he was so well-known and respected for these sequences that he was given much more independence in choreographing them, which led to his dance sequences feeling distinctly separate from narrative portions of the films.
You can find one example of his work here: "By a Waterfall" from Footlight Parade (1933)