Speaking as someone whose attempts at formal dance resemble a man trying to manoeuvre a fridge into a difficult corner, I am in awe of them as can. YouTube is the perfect place to marvel at their genius and to wonder at just how they did it. How does this member of Tip Tap & Toe do that sliding thing at about 0.49 without shooting straight off the end of the dais?
The physical ease of these people is breathtaking. How does Fred Astaire manage to go from speech to song in the space of one sentence without looking embarrassed? How could they film such demanding routines without cuts and edits? They must have rehearsed for weeks before every number.
How did Whitey's Lindyhoppers manage to get through a number like this without somebody getting seriously hurt? This was 1941, long before the invention of either rock and roll or health and safety.
My old Dad knew nothing about dancing but he used to say "you've got to be good to be able to muck around". There's no better example of this than Wilson & Keppel who parlayed one number into a forty-year career. In the days before TV.