Around the same time, Boston was building a symphony hall. American orchestras typically performed in theatres or in opera houses, venues that were often shaped like fans, with the stage as the base of the handle. This design made for good sight lines. But Sabine, when consulted, told the architects to use the European model of the “shoebox” concert hall—a rectangle, which can provide a full sound, evenly distributed among the seats. Sabine also suggested narrowing the balconies and making the stage walls taper inward, to redirect and focus the sound. Materials that reflected sound, such as hard brick, steel, and plaster, were used to make the walls—a counter to the absorption of the seats and the human bodies. A balance of warmth and clarity was achieved. Boston’s Symphony Hall remains celebrated for its acoustics. And the unit of sound absorption is called the “sabin.” One sabin is roughly equivalent to the sound absorption of one of those old Sanders Theatre seat cushions.

When I first spoke with Blair and Scarbrough, in November, 2021, many decisions had already been made. Geffen is a shoebox, and it would stay that way. But the orchestra had been moved forward twenty-five feet. Scarbrough said, “Before renovation, almost thirty per cent of the seats were more than a hundred feet away from the orchestra. Now nine per cent of the seats are.” This wasn’t just about sound—it was about the feeling of closeness, and how that affects one’s experience of music. The seating capacity had been reduced from more than twenty-seven hundred to twenty-two hundred. Scarbrough and Blair said that one reason for the disappointing acoustics of Philharmonic Hall had been the initial failure of the board and the architects to listen to acousticians’ advice. The original acousticians were led by Leo Beranek, who died in 2016, at the age of a hundred and two. Beranek did much important research in the field, including on the acoustics in jet planes, where pilots’ voices were drowned out by excessive noise from the engine. He also designed the acoustics of the United Nations General Assembly Hall, in New York. “It really wasn’t his fault!” Blair said, of Philharmonic Hall’s sound. “They added more seats without even consulting him, and it destroyed him.”

“Well, I wouldn’t say it destroyed him,” Scarbrough said.

Propped against the wall of the conference room where we were sitting was a piece of buttery-looking rippled beechwood, which resembled an old radiator. Scarbrough explained that it was a sample piece of panelling for the hall’s interior: “We gave Gary”—Gary McCluskie, the head architect for Diamond Schmitt—“the percentage of wall surface we needed flat versus articulated. Those numbers were based on studies of historic halls in Europe. They came up with this modified sine curve.” (The architects had also considered oak, but found its lines to be too visually noisy.) “Beechwood was a challenge, because wood is organic, it expands and contracts,” Scarbrough said. “We had the woodworkers give us exact measurements of how big a panel could be so that the wood wouldn’t get cracks. But it was worth it for the emotion of the wood.”

Blair said that, though most old European halls appear to be built wholly of wood, this is an illusion. “They’re mostly plaster,” he said. “In Vienna”—at the Musikverein—“there’s a wood ceiling, but on top of that is a layer of bricks.” Scarbrough added, “The acoustical historian Pamela Clements argues that this was an effort to fireproof the hall,” which, incidentally, contributed to the Musikverein’s marvellous sound.

The unseen elements of Geffen Hall had the opposite effect. Scarbrough explained that the walls were sucking energy out of the air: “In the 1976 renovation, the walls were three-quarter-inch-thick plywood panels, then furring strips, and then insulation.” Bass sounds vibrated the plywood panels, leaching the strength of the bass from the music; lacking bass, music can sound anemic, and diminished in complexity. The new beechwood panels will adhere directly to the masonry. On one of his weekly visits, Scarbrough checked the wood panels for how rigidly they stuck to the wall; he recommended changing the one-eighth-inch coating of adhesive to a three-sixteenths coating—insuring a tighter seal and reducing vibration.

The architect Gary McCluskie—tall, thin, and stylishly dressed, like an architect—took me on a couple of hard-hat tours of the hall while the renovation was in process. McCluskie’s team has also designed concert halls in Montreal and St. Petersburg. “The hall is itself an instrument, right?” he said. “It’s made of wood.” McCluskie showed me how the floor had been reraked—increasing the slant from four degrees to seven degrees—to provide better sight lines and to avoid the music running into the flat wall of the audience. The side tiers now had seats that angled toward the stage, as if embracing it. He explained that the stage would have risers and platforms that could be rearranged, depending on how the musicians might use the space, and on whether a performance would include a chorus.

We were looking out at walls of plastic sheeting; something enormous was being hoisted up above the stage so that adjustable absorptive banners of wool serge could be installed. “One thing that’s really interesting to me is the psychoacoustics,” McCluskie said. “Restaurateurs know about this, of course—that the presentation of food affects the way it tastes.” The architects had to make the space warm and welcoming, so that the audience would feel connected to the musicians. For that reason, McCluskie had pushed for the reraking of the floor. “It’s just three degrees difference, but it really affects the sense of closeness to the musicians,” he said. The architects also changed the way that the audience circulates through the building. “With the old hall, it was difficult to even find the entrance, unless you already knew where it was,” McCluskie said. They wanted the hall to feel welcoming to everyone, not only to those people who were—in whatever way—in the know.

It’s the same hall—the same box—but it’s also a near-total transformation. The ceiling is relatively untouched, saving time and money, but it will be experienced differently. “It wasn’t adding anything to the old hall,” McCluskie said. It was simply a dark vault. His team designed a “sound-transparent” mesh to overlay the ceiling: a hand-bent steel grid, with a clover pattern, that catches the light. The seats are upholstered in a fabric with a fallen-petals pattern, a visual echo of the trees visible through the now mostly glass front of the building. “When the fabric for the seats first arrived, it was the wrong thickness—we were in a total panic,” McCluskie said. Seating is a major source of sabins—of sound absorption. “But it turned out the samples they sent just didn’t have the proper backing on them.”

So much of concert-hall design is a matter of chance. Scarbrough talked about working on a concert hall in Nashville. “At the outset of the project, I travelled with the board to see seven concert halls, in five cities, in six days,” he said. One of those was the Musikverein, for an afternoon concert of Dvořák’s Requiem. “And, just as the closing chords were sounded, the sun came around the west of the building, and the room flooded with golden light,” he said. “It was everything—music, architecture, acoustics, the natural environment.” And that is why the Schermerhorn Symphony Center, in Nashville, has windows.

Deborah Borda was the President and C.E.O. of the Los Angeles Philharmonic when the Walt Disney Concert Hall, a silver Frank Gehry building whose shape bears a resemblance to an Everlasting Gobstopper, was being constructed. “We didn’t really know what the sound would be,” she said. “You do all this planning, but . . . Well, I will never forget sitting in the audience section with Frank and Yasuhisa Toyota, who was the acoustician. And Esa-Pekka Salonen was conducting. We were so scared. Frank and I were holding hands. Then Esa-Pekka turned around and said, ‘Ladies and gentlemen, we have a bass section.’ Frank and I cried.”

Jaap van Zweden, the conductor of the New York Philharmonic, wears all black, which draws attention to his expressive gray eyes. He has a relatively thick Dutch accent, and tends to punctuate his speech with “well, yah” and with the placing together of his hands as a form of punctuation. “Young people listen with their eyes,” he told me. “This hall needs to be not just for us but for the next century.”

Van Zweden explained that, because the orchestra travels, it is accustomed to the challenge of acoustics changing all the time. “Sometimes when we arrive somewhere we don’t even have the opportunity to rehearse in the space that we will play,” he said. “Each hall is an instrument, and, if a hall does not have good acoustics, I say that the orchestra must make their own acoustics.” Acoustics, he said, is a living thing. If a sound is “dry,” a little curt, then you can play over the rests for continuity. “If the acoustics are naturally excellent, you don’t need to dig into the strings for a bigger sound. It’s like painting in oil paint, versus a watercolor,” he said. “In a good hall, you can play with both.”

Van Zweden cited Shostakovich’s Fifth Symphony as an example of a piece that can test the acoustics of a space. Some parts are very loud, and some very soft—does a hall let you hear both extremes? “That piece has very powerful moments when you hold your breath—that’s so important,” he said. “How can you make thick sounds, thin sounds—this is what we ask of a space.” Van Zweden also, in his own way, emphasized the power of psychoacoustics. “In my parents’ bedroom, when I was a child, they had a piano next to their bed. That sounded pretty well, I really liked those acoustics,” he said brightly. He added that some of the best halls from an acoustical perspective include Cleveland and Boston, and that “there is a certain magic touch that only comes with time. Like a Stradivarius violin—it’s a fantastic sound, plus history.”

My initial conversation with van Zweden was in June. At the tuning rehearsals, which would begin in August, the orchestra would play selections from various pieces to test aspects of the hall’s acoustics—its range, its clarity, its reverberance, and also how well the orchestra members could hear one another while playing. “That is when we will see,” van Zweden said. “It will be dynamic, we will be changing things.” He would start thinking about whether, say, to place the second violins on the outside, as in the Viennese style, or whether to put the cellos or the violas there. The distinctive sound of each section of the orchestra—the brass, the strings, the woodwinds, the percussion—would carry, or not, in the space.

Covid had been very difficult for musicians, van Zweden said. He had spent much of the past two and a half years at home in Amsterdam. He lamented having been unable to develop his relationship with the orchestra through shared music, since he had only begun working with the Philharmonic in 2018. When the music world opened sufficiently for the Philharmonic to play some concerts—though not in their home space—he was proud, he said, that “our audience came with us.” Musicians are meant to be sharing their music.

But van Zweden also valued being home, with family, in the early days of the pandemic. He focussed on his health, and lost seventy pounds. He spent time with his father, who is ninety-four. He even revived his father following a heart attack, doing chest compressions until an ambulance arrived. “My father still plays the piano every day,” he said. “And a few times a month he still puts on concerts in small halls in Amsterdam.”

“By the time of the tuning rehearsals, it’s entirely in the ears,” Scarbrough said. “We’ll do measurements to document it, and measurements get you to ninety per cent, but the ears get us that last ten per cent.” In the most general sense, Scarbrough and Blair would listen for balance among the different sections of the orchestra. Scarbrough said, “The magnitude difference between a brass instrument and a woodwind is quite extraordinary, but, if the hall balances effectively, the conductor can work with that.”

They would also listen for timbre. “Does an oboe sound like an oboe? The woodwinds produce similar tones and frequencies, but they have subtly different timbres,” Scarbrough said. The trueness with which the hall would reflect the oboeness of oboes, the piccoloness of piccolos—that would be another measure of success. Scarbrough went on, “We’re also listening for blend and transparency. You can have tremendous blend but then not be able to pick out individual instruments. You can have tremendous transparency, but with the orchestra sounding like a hundred and five soloists.”

“Try to play with a kid whose parent isn’t too chatty.”

Cartoon by Ellis Rosen

Blair said, “What we really want is an orchestra that can hear each other and perform together even without a conductor.” This is not only a goal but an occasional practice: the New York Philharmonic usually plays the overture to “Candide” with no conductor, in memory of Leonard Bernstein, who composed it.

“And we want it to sound good from many different seats in the hall,” Scarbrough said.

“And, to be completely honest, we have to make sure Row N is perfect,” Blair said. “That is where music critics tend to sit,” he added, with a look of mischief.

The hall is “a chameleon,” Scarbrough said. Changes to the acoustics will be made after the tuning rehearsals, but also sometimes in between performances. Some of the main mechanisms for these literal fine-tunings are the risers, the seating arrangements of the orchestra, reflectors above the stage, and the wool-serge banners. The doors around the stage have slots for panels that can reflect or dampen sound. Scarbrough said, “If they are doing something special with a lot of amplified sound, for example, they can pull out the diffusive panels and put in the absorptive ones, to dry up the stage so an amplified performer can hear themselves.”

The banners are beige, so as not to attract notice, and can be deployed in numerous ways, though they are used most often for amplified sound, such as at film screenings and pop performances. Scarbrough said, “I used to put in some pre-settings and label them ‘classical,’ ‘romantic,’ ‘contemporary,’ etc., but then you’d get into these questions like, Is Beethoven’s Ninth Symphony crossing into ‘romantic’?”

Blair added, “And Debussy is not the same as Mahler.”