Jack Quartet, Tuesday, Nov. 13, 8 p.m., $15, The Fruit, Durham, www.dukeperformances.duke.edu

“It’s actually sort of hard to get a space dark,” says John Pickford Richards, a violist in New York’s JACK Quartet. “Even if there’s just an exit sign in a room or, like, a wireless router, after fifteen minutes in the dark, that becomes as bright as the sun, and you can see everything.”

Richards would know. The JACK Quartet has been performing in darkness for nearly a decade now, specifically for a pair of quartets by Austrian composer Georg Friedrich Haas that are meant to be performed in the dark.

“What we strive for,” Richards explains, “is the kind of darkness where you wave your hands in front of your eyes, and you don’t see any difference.”

Performing in that kind of darkness provides certain logistical challenges. Musicians rely on their eyes for so many things, large and small; in the dark, they can’t see their music, their bandmates, or even their instruments. Even the simple act of placing the bow correctly on the strings becomes a leap of faith—a small shift in the contact point has a profound effect on the resulting sound. Musicians rely on visual cues among each other to align an entrance or agree on a beat, which also goes out the window when the lights go out.

“If I know we’re supposed to hold on to something for five seconds, then do something else. If I have my vision, I am waiting for five seconds—I’m aware of the time, but I see when we move on,” Richards says. “Without the vision, the same thing happens, but the way I know to move on is a much more felt and shared experience. There’s no leader in that moment. We’re all literally on the edge of our seats, listening as intently as we can to each other. It’s a game of chicken, a little bit.”

Since its founding in 2005, the JACK Quartet—violinists Christopher Otto and Austin Wulliman, violist Richards, and cellist Jay Campbell—has built a reputation as a fierce proponent of contemporary classical music. The ensemble revels in the most rhythmically intricate, conceptually dense, or sonically challenging scores around, demonstrating the inherent musicality and beauty of all of these works. For them, Haas’s challenge of playing in darkness is just another day in the office, one difficult compositional instruction amongst many. And, as with so many of those instructions, the payoff is worth it in the unexpected and intense musical experience it creates.

When the JACK first appeared at Duke in 2012, they performed Haas’s third quartet, written in 2001 and subtitled “In iij. Noct.,” in a black box theater on campus. The darkness was thick and total, save for a single, faint pinprick of light sneaking in through the door. Ethereal timbres slowly emerged from the four corners of the room, a mix of gentle knocks, screaming harmonics, grinding noise, sumptuous chords, and glittering melodies.

For that work, Haas gets around the constraints of darkness by writing the piece as a highly structured improvisation. He gives players instructions for various musical scenarios as well as ways for the players to invite each other to move between them. Richards describes it as “a game of improvisation with a bunch of rules to be manipulated and broken, and there’s a system for every response to what we do, so every performance is different.”

The work ends with a wobbly reimagination of music for the Catholic Tenebrae service by the late-sixteenth-century composer Carlo Gesualdo. The 2012 performance at Duke was sumptuous and wholly engrossing. I found myself involuntarily turning in my chair, trying to absorb all the different possible permutations of the music as it cascaded around the room. Robbed of my sight, I noticed my ears becoming so much more attuned to every stray flicker of sound, and I found myself becoming a listening machine. I was almost disappointed when the lights came back up at the end of the show.

Over the years, JACK has performed Haas’s third quartet dozens of times, enough that they caught the attention of the composer himself, and they quickly became friends and collaborators. He has since written two pieces for them: the conventionally lit eighth quartet in 2014 and a return to the darkness in the ninth in 2016. This new work with the lights out differs from its predecessor in a few critical ways. Where the older work was built around improvisation and chance, this new piece is almost entirely through-composed, meaning the quartet had to memorize all forty-five minutes of it. Instead of splaying the quartet around the room, Haas places the group sitting in a regular quartet configuration. And, most importantly, Haas bases much of the harmonic language on a tuning system called “just intonation,” one of JACK’s specialties.

Much of Western music from the past two hundred and fifty years is written in “equal temperament,” a tuning system where the space between any two notes on the piano is the same. It’s a compromise that allows for greater flexibility to move between different keys at the expense of harmonic purity. Just intonation flips that compromise on its head, using the overtone series with its simple mathematical ratios as its base. The space between any two notes on a piano in just intonation would vary wildly, making it hard to move between keys. But a chord tuned in just intonation sounds uncanny, with all the pitches locking together to create a single, pulsating mass. Thus, the same chord in equal temperament and in just intonation would sound totally different, like distant dialects of the same language. To say that the JACK Quartet is obsessed with just intonation would be an understatement.

“We are sort of backwards,” Richards says. “We prefer just intonation, and it’s equal, tempered space that messes with our brains. We actually don’t even allow ourselves to go into that world too often.”

In the ninth quartet, Haas pits the two systems against each other, juxtaposing a melody in one space with harmonies from the other, and visa versa. The results are a towering, trembling drone that constantly folds in on and reinvents itself.

This is where darkness proves so critical to experiencing and understanding the piece. Every odd harmonic shift takes on an extra charge, a vivacity, a profound newness. There are no cues to grab hold of from the quartet or even from your neighbors in the audience. In a way, the darkness provides a kind of visceral purity analogous to the harmonic purity of those just intonation chords, something that must be experienced to be fully understood.