On a recent weekday, Gino Francesconi, the hall’s archivist, took me on a behind-the-scenes tour to answer this question. We started backstage, where we rode a service elevator to the sixth floor. We then passed through a few rooms, each littered with cases for tubas, trumpets and trombones, until we reached a door that was labeled, “Hard Hat Required.” Mr. Francesconi reached into his pocket and fished out a sizable ring of keys.
Any time an archivist has to unlock something, you know you’re in for a treat.
The key clicked and the door opened. The first thing I noticed was the door’s 5.5-inch thickness, designed to keep noise from entering the hall from a nearby practice room.
As we crossed into near-darkness, Mr. Francesconi turned to me. “You have to walk very quietly,” he whispered. We were now directly above the stage, where a high-school orchestra from Georgia was rehearsing for a concert that evening.
We tiptoed along a metal catwalk, which turned at bizarre angles and had stairs in seemingly random places. At one point, we had to step over a steel beam, and then do the limbo under a duct vent — all while trying our best to remain silent.
Mr. Francesconi pointed out the graffiti on many of the beams and poles; scrawling your name up here is a longtime tradition of the hall’s stagehands.
He then flipped a light switch, illuminating a vaulted ceiling — hidden to patrons below by the auditorium’s plaster ceiling — of Guastavino tile, similar to the “Whisper Gallery” at Grand Central Terminal and the abandoned City Hall subway station. From here, we could see the metal structures that supported the two circles of lights below us, the bulbs’ cords dangling at regular intervals, near pathways deviating from the catwalk. Stagehands simply pull the lights up by these cords and change the bulbs.
Before we turned around, Mr. Francesconi called my attention to a small opening in the floor, through which I could see the orchestra, directly below. The players and their instruments appeared in miniature, but thanks to the hall’s acoustic design, their sound was as crisp from this unusual vantage as from any seat down below.
An earlier version of this article misspelled the name of the tile on a vaulted ceiling inside Carnegie Hall. It is Guastavino tile, not Gustavino tile.