Many dogs are frightened by very sudden noises such as fireworks or gunshots, but tolerate other noise such as crowds or music well.
Most dogs like attention and associate crowds with extra petting and attention, and perhaps the odd treat.
A minority of dogs are frightened of anything, but most enjoy public events.
I suspect it comes down to the individual dog, and most people know their dogs well and are sensible. I suspect our two are exceptions ... they indeed LOVE crowds (and, yes, a greyhound on a rush hour tube does get a lot of extra attention and petting) - however, they are
not frightened by fireworks, amazingly; I was really concerned the first time Gyp wanted to go out for a wee on bonfire night - need not have been; both she and Billy ignore the bangs that make me jump. Nothing wrong with their hearing - they can hear a lead being picked up half a house away!