A - In Brazilian culture, people are first and foremost defined by their relationships to other people. While the average American, Australian or European sees himself or herself mostly as an individual endowed with universal rights that may not be trod upon, Brazilians see themselves as nodes in a social network, in which each person is defined by who knows them and whom they know. Being seen as a nagging neighbor would damage their social relationships, leading them to think twice before complaining about anything. Thus, in a situation where a gringo would undoubtedly act to see his or her rights (to nightly silence, to a swift service at the bank, whatever) respected, a Brazilian will try instead to establish a good (i.e., enduring and mutually profitable) social relationship with his or her neighbors. He will endure the loud music, and in doing so the people responsible for it will become more or less connected to him and he will be able to expect them to endure his or her own unpleasantness, doing him small favors when requested, etc.
It is not a straight exchange, as, ideally, the relationship will never end. He will not be bartering his endurance of a single night of loud music for one given favor, but, for instance, he will expect a discount at the entrance fee if he ever decides to join the ball. In other words, he will endure the loud music in exchange for a permanent relationship in which he can expect a special treatment, just as he is giving the party people a special treatment.
At the same time, a strong notion of hierarchy comes into play: Brazilians do not see themselves as the equal of every other man, as there are people who are much more powerfully connected in the same networks he inhabits. Let us not forget that the Brazilian equivalent of "money talks and BS walks" is "mais vale ter amigos na praça que dinheiro em caixa" ("friends in the marketplace are worth more than cash"). Thus, in the bank (or if the loud party is thrown by someone powerful), to disturb the social order by complaining loudly would be seen as a social blunder, unless the complainer is more powerful than the bothersome party. If that is the case, the blunder will be the bank's, for not giving him his due respect.
Thus, if the bank manager is a friend, the average Brazilian will expect his or her friend to fish him out of the queue and take personal care of his or her business: the bank manager's power becomes his own because they are connected. If he knows nobody at the bank, he is powerless and will not at all see a swift service (perceived as a kind of special treatment, as, looking around, he notices nobody has it!) as his right. On the other hand, he will more often than not chat with the people in the queue, complaining about the service as he would complain about the weather, establishing thus a relationship with them, "fellow underdog". Then, if he arrives the next day in a store and the store manager is the guy whom he met at the bank line, he will expect some kind of special treatment from him (anything from a smile to a good suggestion of what is the best buy), as they are already connected. Needless to say, if you want a good life in Brazil, don't forget your Dale Carnegie!
For further reading, I would recommend a book by the famous anthropologist Roberto daMatta, called "Carnival, Rogues, and Heroes"