Hard-headed, conservative businessman goes head-to-head with outrageous singer from California/Europe. Cather doesn't pull any punches--or, in other words, she doesn't bother with too much subtlety. The man is not just compared to rock (or rather, brick, since rock is probably too natural), but works in coal--though of course he doesn't actually work with his hands. And he's so anti-doing things that he didn't even go see this singer when he was in Paris, even though there's nothing to do in Paris. Add in a rim-shot and you've got a comedy routine there.
Though the story begins with the drab businessman being dragged along to a concert, the bulk of the story is actually the dialogue between the two: they happen to be taking the same train. The singer is outrageous but also very smart and charming and honest, as when she notes that the culture has convinced even her that drab office-working stenographers have some better claim to morality than she does.
Which leads to the final prank: she leaves him a gold slipper, which starts as an insult and becomes a cherished item for him, a reminder of youth and happiness.
But let's be clear on one thing: though this singer may be a good singer who, like Elvis, is proud to support many people (both family and entourage), she seems to have her mind on the main prize as much as the businessman. As we see at the beginning, most of her affectations are chosen so that she becomes a household word. In other words, a little outrageousness is just the thing to separate the rubes from their money.
Or as The Onion noted about Green Day's rock-musical American Idiot,
The protagonist ultimately realizes that fulfillment doesn't come from rigid societal conformism, but from a mild, inoffensive brand of nonconformism that is easily digestible—even widely marketable—to the masses.