PITTSFIELD — It's the unseen, but very much heard, performance at Barrington Stage Company's Boyd-Quinson Mainstage these days.

As "Into the Woods" actors stomp and slide on the platform above them, 11 musicians mind their instruments below, following conductor Darren R. Cohen's lead as he awaits cues and navigates Stephen Sondheim's score to the renowned musical. Poking through a rectangular stage cut-out, Cohen's bobbing head is one of the audience's only visual reminders that a cramped group plays below the scenes.

"You're not the primary thing, but you're making the machine work," French horn player Jean Jeffries said before a recent Tuesday night performance.

The orchestra pit is part of a compact underground lair at the Pittsfield theater company's largest venue, which will be hosting "Into the Woods" through July 13. Entering down a Union Street stairwell, staffers and creative types quickly encounter dressing rooms; offices for stage, production and company management teams; and a "green room" with a cot and coffee. About 45 minutes before curtain on this Tuesday night, Cohen was roaming the designated lounge area. The play's song list was taped to a wall near him, displaying the numbers' titles and the characters involved in them. "Cinderella at the Grave," for instance, would open Act 1's second scene and include the narrator and Cinderella. Occupying six typed pages, the dozens of songs conveyed the hundreds of musical cues — a hit, a tap, a bean-counting — that Cohen would have to detect throughout the evening.

"I'm constantly looking and listening," he said later.

While Cohen need only tilt his head a tad to see the stage, the musicians must rely on their conductor, who stands above them on a platform, to convey the story's timing. For instance, the play opens with the narrator center-stage. Once he points at Cohen, a high-pitched "ding" of percussion must immediately follow. And after a brisk beginning, Cohen must halt the music when Florinda slaps Cinderella for twisting her hair too tight; an errant note can ruin the moment's shock.

With microphones, cords, music stands and poor angles, some musicians cannot see Cohen in the dim room, glancing at a monitor instead. The musicians form a "C" around Cohen; assembling them is the night's first challenge. Percussionist Deane Prouty, keyboardist Trevor M. Pierce and bassist Jon Suters were stationed to Cohen's right, the farthest instrumentalists from the door.

"Sometimes, that comes in over our heads," clarinetist Lyndon Moors said of Suters' upright bass.

Moors was part of an inner ring that consisted of Gerald Lanoue (bassoon), Zachary Robarge (flute and piccolo), Susan French (viola), Courtney Clark (violin) and Peter Zay (cello). Like many of the group's members, Moors had arrived roughly 30 minutes before the show's start. Every time they enter the pit, musicians pass "rules" on the door. Some of these principles plainly advertise the group's wry humor.

"If the ensemble has to stop because of you, explain in detail why you got lost. Everyone will be immensely interested," one rule reads.

The orchestra was quiet, but calm in the minutes leading up to the show. Jeffries, for example, was knitting a sweater for her son. The horn player relishes the opportunity to play out of the audience's view. At standard gigs, horns often receive a lot of solo opportunities and attention, but working on musicals allows Jeffries to simply revel in the music.

"I always enjoy playing in pits," she said.

Trumpet player Jeff Stevens was sitting next to her. The former Monument Mountain Regional High School teacher was one of multiple local educators in the pit.

"I enjoy the creative process of all these shows," said Stevens, who has been involved in BSC productions for more than two decades.

Cohen has a similarly long relationship to BSC. He has worked on a number of Sondheim productions, but this show has been his first go-round with "Into the Woods."

"There's no style. You can't say it's a period piece. Is it contemporary music? It's just his, and it's interesting," Cohen said of what makes Sondheim's score special.

Musical theater's excitement and spontaneity drew Cohen to his current line of work. During his studies at the Eastman School of Music, Cohen realized that classical was too boring for him.

"My personality is not disciplined for that world. I kind of found musical theater, and I thought, 'I could take the same training and just put it in a more fun environment,'" he recalled.

After graduating, Cohen landed work almost immediately as a pianist in a Broadway production of "A Chorus Line," a precursor to a handful of gigs on the Great White Way. He's based in New York City, but appreciates his eight weeks in the Berkshires every summer.

"It's a great home away from home," he said.

Taking his position behind a music stand and raising his arms, baton in one hand, Cohen bore the expression of a seasoned veteran during the play's early moments as legs and feet moved remarkably close to his head. He said that he hadn't been kicked yet during this production. Spectators are often concerned, though. In a BSC production of "The Pirates of Penzance" in 2016, a sword fight took place over Cohen's head.

"It was so choreographed, I never worried. But the audience, every night, would say to me, 'Oh, my God, the whole show we were so worried that you were going to get hit!' So, they actually had to move the stage in because the audience was actually focusing too much on me getting hit," Cohen recalled.

Generally speaking, wrong notes or lyrics are more apt to make Cohen wince than rogue limbs. It happened a few times on this night.

"I don't hide it well. It's not by any means the end of the world, but it's just very hard for me to hear it and not respond," he said afterward.

A vital part of Cohen's job, however, is to adjust to the inevitable timing shifts that will occur during even the most clinical live performances. Throughout the show, Cohen often held up a fist, the signal for musicians to "vamp," or to repeat that part of the song until the play catches up.

"It's kind of like a train conductor," Cohen said of his role.

Since the orchestra is on the smaller side, Pierce helps bridge sonic gaps with his keyboard's effects, perhaps adding some strings where necessary.

"His job is to enhance because I don't want it to sound empty, but I don't also want us to sound like something we're not," Cohen said. "We can't sound like 20. But it's enough to just fill in some space so it sounds more cohesive."

Hearing music in the pit is different than hearing it in the theater. The audience listens to a mixed version of the song that the sound engineer, in this case Eddy Mineishi, creates. So, when many parts coalesce in a song such as "Last Midnight," the one Mykal Kilgore's witch belts near the end of Act 2, it doesn't sound quite as polished in the pit as it does in the house. But in the clashing fairy tales of "Into the Woods," complete harmony isn't usually the sonic goal, anyway.

"I like that there's so much dissonance in it," French said of Sondheim's score during intermission.

There's also humor. Just as some in the audience laughed when the witch squashed a bug, a few in the orchestra chuckled. But for most of the night, this musical bunch was all business. As the actors took their bows at the end of the performance, the orchestra kept playing. After nearly three hours of performing late into the night, a matinee was on the horizon.

"Thanks, everybody," Cohen said. "Two o'clock tomorrow."

Benjamin Cassidy can be reached at bcassidy@berkshireeagle.com, at @bybencassidy on Twitter and 413-496-6251.