The part of the novel to which you are referring is Chapter One, when Madame Nilsson's appearance in the Opera House has drawn a "particularly brilliant audience", in the words of the society pages. There is much discussion of the habits and behaviors of the very wealthy and high-born people of New York at that time -- not the least of which is their eagerness to leave their amusements "even more
quickly than they want to get to it."
The American "aristocracy" arrive in their personal coaches, or in a respectable hired carriage from Brown's. They sit in boxes high above the orchestra floor, which not only gives them the advantage of a superior viewpoint per the crowd of relative rabble below, but also gives them a better view of the action onstage and, most importantly, of the comings and goings and activities of each other. The boxes provide a level of privacy, if engaged by a small group, family, a club (such as Newland Archer's) or an individual, and they also allow a level of publicity to this privacy, because everyone has opera glasses (fancy binoculars) to peer at each other. Every aspect of dress, appearance, and behavior is noted and commented on in this elite group.
The main character, Newland, arrives late, because it was not "the thing" to arrive on time to the Opera in New York in those days. "and what was or was not "the thing" played
a part as important in Newland Archer's New York as
the inscrutable totem terrors that had ruled the destinies
of his forefathers thousands of years ago."
Newland watches the opera, arriving at his favorite moment, and the arbitrary nature of the rules that governed some of the social conventions of Newland's class are commented on my Wharton: "since an unalterable and unquestioned law of the musical world required that the German text of French
operas sung by Swedish artists should be translated
into Italian for the clearer understanding of English-
This commentary on the scene and the people continues throughout the chapter, especially when the arrival of Countess Olenska causes a stir. She is an example of an exception to all the social rules, primarily because she has a strong family behind her to flout convention. Newland, who up until this moment had been a slave to the conventions of his class, becomes fascinated with the Countess, and the main conflicts of the novel stem from this moment of her appearance at the Metropolitan Opera.
Source: Literature Network http://www.online-literature.com/wharton/innocence/1/