Four major theaters anchor the Berkshire summer season: the Berkshire Theatre Festival in Stockbridge, Shakespeare & Company in Lenox, Pittsfield’s Barrington Stage Company and the Williamstown Theatre Festival. I’ve been covering their shows for a couple of decades now, but usually as a critic, sitting front of house reviewing what’s happening onstage. This summer, I’m digging a little deeper, spending a full day with each troupe to look into some of what happens backstage as well.

Starting with the longest-established of the quartet, the 82-year-old Berkshire Theatre Festival, which I dropped in on last week. In the lobby of the mainstage playhouse, a collage of famous faces documents the generations of stars who have passed through over the years, from Cagney to Pacino. During the summer season, the theater carries a staff of 220, including actors, directors, designers, technicians, support personnel and a cadre of young interns and apprentices.

BTF’s second stage, the Unicorn Theatre, is tucked into a converted barn it shares with the company’s scene shop. I’m starting my day here, with a matinee performance of K2. On the theater’s outdoor patio, Sara Deviney is tending the concession stand. A musical-theater major at Emerson College in Boston, she’s spending the summer here as one of the company’s 26 acting apprentices. They take classes with the company’s professionals and understudy or play walk-ons in mainstage performances, or perform in the company’s children’s theater show.

She tells me she’s here not just to learn techniques that aren’t taught in her college program, but to broaden her horizons: “I can meet people from different backgrounds with different takes on theater.” And even though there’s a tuition fee for the experience of working 12-hour days, she finds it a bargain. Her summer alternative was an unpaid internship in New York, with the city’s expenses. “So I figured I might as well be here,” she says, “getting all of these experiences, working with all these wonderful people, plus getting a place to live and getting fed three meals a day.”

K2, by Patrick Meyers, takes place on the world’s second-highest mountain, where two men are trapped after a fall. Scene designer Kenneth Grady Barker’s set is a realistic-looking three-by-five shelf of rock on a monolithic cliff face. The short, intense play pairs hyper, talkative, terrified Taylor with laconic Harold, who has an almost Zen-like understanding of their predicament. Greg Keller and Tim McGeever’s performances are convincing and affecting, an illustration of the constantly astonishing caliber of work that summer theaters are capable of in the pressure-cooker two-week turnaround of productions.

The scene shop is alive with activity and the buzz of Skil saws. In his cubbyhole office off the main floor sits John Traub, the company’s associate technical director and a grad student at Boston University, now in his third summer at BTF. He describes the process of turning the scenic designers’ drawings into finished sets: “We have three to five days to get from design to technical drawings for the shop staff, so they can build things that are what the designer wants aesthetically, but also safe and strong and do all the magic theater tricks they have to do. Then we have less than two weeks to build everything.” After the final Saturday performance of each show, “We strike the set from 10 p.m. to midnight, then the lighting crew will come in and re-hang all the lights, and then we come back on Sunday morning and basically have nine hours to put up the new set.”

On K2, Traub also worked as a technical advisor. “I have a lot of rigging and climbing experience, so I was really a rigging advisor,” he says, “as well as loaning my personal climbing equipment to the show.” During the play, the actor playing Taylor climbs up the cliff face to retrieve a rope. Traub reveals one offstage secret: “One of the assistant stage managers is at the top, above the stage, wearing a climbing harness, belaying and working the ropes.” Though the play takes place in 40-below temperatures, “there’s a crew member up there, sweating in 100 degrees.”

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Opening this week in the Unicorn is Samuel Beckett’s tragicomic investigation of existential immobility, Endgame. During my visit, it was rehearsing on the company’s Lavan Campus, a former private school and summer camp up the road from the main campus.

Endgame‘s four characters are all incapacitated in some way—one in a wheelchair, unable to stand, one unable to sit, and two legless, living in side-by-side trash barrels. The two trashcan occupants are extremely old, but played here by two young actors, Randy Harrison and Tanya Dougherty, in symbolic whiteface makeup. Director Eric Hill says, “One of the themes of the play is that the end is in the beginning, so they’re old but they’re in a circle, coming back around.” Besides, he adds, “For really old people, squatting in those barrels would be too hard—it’s really hard work for the young people.”

Hill has been working with BTF for 16 years, since his wife, Kate Maguire, became artistic director in 1994. Although she makes the final decisions on repertoire, the directors—many of whom, like the actors and designers, come back to work here year after year—have critical input on plays they’d like to work on. “I don’t come to a play with any preconceived notion,” Hill says. “I try to let the designers tell me more about what they want. I’ve always got a vision of the play, but how that fits into a design and a concept is really more of an evolutionary process.”

This is Randy Harrison’s sixth season at BTF. “As an American actor, it’s almost impossible to find a community like Kate fosters here,” he says. “You really grow as an artist when you can work with the same actors over and over again. It’s a chance you don’t usually find. And of course it’s the Berkshires, the best place to be in the summer.”

Next door, the second mainstage show, scheduled to open July 13, is in its first week of rehearsal. It’s The Guardsman, a marital comedy by the Hungarian playwright Ferenc Molnar about an actor who puts on an act—pretending to be a Russian officer—to test the fidelity of his notoriously unfaithful actress wife. It stars Michael Gill and Jayne Atkinson, a real-life husband-and-wife acting team.

When I enter the rehearsal room, director John Rando is giving notes on the Act One rehearsal that just ended. Most of them concern problems with tiny but crucial bits of comic business: handling a cigarette with gloves on, getting a laugh with a rattling tea tray. When they start in on Act Two, Rando asks, “Shall we plow through, or stumble through it?” and gets his answer from one of the cast: “Let’s stumble—that’s what you’d get anyway.”

During a break, Michael Gill confides that the Guardsman role could be “the most difficult part I have ever played. There is so much going on with him on so many different levels. There’s the basic jealousy that is the driving force in what he’s doing. There’s also the drama diva in him, who overperforms his emotions. And then he has to carry all of that into another character, and convince his own wife that it’s not him. It’s kind of endless, and it’s fascinating.” Like so many other actors here, Gill has a long history with the company. He first appeared here in 1990, but way before that, “I used to usher here when I was 13 or 14 years old.”

Kate Maguire is rushing from a board of directors meeting to a reception with supporters of the theater. Joining her in transit, I ask her about the company’s current promotional self-description, “Theater that matters.”

“I don’t want to do theatrical entertainment for the sake of entertainment only,” she says. “Part of the reason we have nonprofit status as an ‘educational institution’ is that we are meant to educate, we are meant to produce great work, like Beckett. I’m also trying to pay attention to the word ‘festival’ in our name. I want to recognize that audiences come for different reasons. I love the idea that you can see Molnar at the same time you can see Beckett.”

Last year, the national economic situation forced a 20-percent cut in BTF’s budget. The company ended the season in the black, but has not increased its budget this year, aware that the economy may not get better for years. (See also StageStruck in this issue.)

One possible symptom of caution may be seen in the fact that the first two shows of the season have a total of four actors. The opening show on the mainstage, The Last Five Years, is also a two-hander, a kind of song cycle with a story. Or rather, two stories. Jason Robert Brown’s musical follows the course of a relationship, but from two different directions, simultaneously. Jamie’s story starts when he meets Cathy—he a writer on the brink of success, she a struggling actress. Cathy’s starts at the end of the relationship, five years later, and moves back through the heartache to the hopeful beginning.

Anders Cato’s production is set in a symbolically blue-gray New York studio apartment. A five-piece band is seated in shadow upstage, unseen participants in the two characters’ trajectories. Paul Anthony Stewart and Julie Reiber are both good actors with strong legit voices, which are more effective in the score’s tender songs and moments of understated emotion than in the numbers that try to be bigger than they should be.

Tonight’s ushers, as every night, are volunteers who get a free seat in exchange for taking tickets, handing out programs and picking up after the show. “Just about all of our ushers this year are people who have volunteered with us in the past,” house manager Tara Young tells me. “Some have been here for 20 or 30 years. They feel really connected to the theater. It’s nice to have people who are dedicated like that.”

That’s the recurring refrain I’ve been hearing all day. As Eric Hill put it, “I like working with actors I’ve worked with before. I like building a repertoire, building relationships, and finding a home in a very good place that has a purpose—to produce meaningful plays rather than just summer theater. That’s fun to be a part of.”

Berkshire Theatre Festival: Through Sept. 4. Seven productions on two stages, plus family programming and Friday lecture/reading series. East Street, Stockbridge, (413) 298-5576, www.berkshiretheatre.org.