NEW YORK — “Why did I say yes?”

Joan Baez is looking quizzically at her one of her closest friends, Karen O’Connor. The two are telling the story of how they met in 1986, when O’Connor was busy starting her career as a documentary filmmaker and Baez was busy . . . being Joan Baez. O’Connor, who was living in western Massachusetts, heard that Baez would soon be performing in Northampton, so she wrote and asked for an on-camera interview.

“Why did I say yes?,” therefore, isn’t a rhetorical question. “You didn’t,” O’Connor tells Baez. “Jeannie read the letter and liked the letter.” (“Jeannie” is Jeanne Triolo Murphy, Baez’s longtime business manager.)

“I remember nothing, of course,” Baez says with a smile, “except sitting across from Karen.”

And here she is again, sitting across from Karen - this time in her favorite room of her favorite hotel, which happens to be next door to the Beacon Theatre, where she gave her final New York City concert in 2018. That performance is one of the pivotal moments in “Joan Baez I Am a Noise,” a documentary O’Connor co-directed with Miri Navasky and Maeve O’Boyle that opened in theaters in October and will be available on demand Tuesday.

Whereas most journalists and documentarians would shy away from attempting to create a genuinely candid portrait of one of their best friends, O’Connor says “I Am a Noise” “wouldn’t be this film if not for the friendship.”

For one thing, it wouldn’t have included footage of Baez’s mother, Joan Bridge Baez, and sister Pauline Baez Marden, both of whom O’Connor filmed before they died, in 2013 and 2016, respectively. “Mom loved her,” Baez says of O’Connor, who became close with the entire family. “And it’s worth mentioning that Pauline would never get in front of a camera for anybody, not for a still photograph or anything. She just trusted Karen.”

Trust informs nearly every aspect of “I Am a Noise,” which includes some surprising details of Baez’s life, including audiotapes of her therapy sessions; letters she wrote to her family when she was becoming unexpectedly famous; drawings she made while uncovering past traumas; and disarmingly intimate present-day scenes filmed at home and on tour. “People will say, ‘Joan Baez is so courageous,’” Baez says mordantly, recalling her civil rights activism, speaking out against violent dictatorships and enduring a bombing raid while visiting North Vietnam in 1972. “’She had courage when she faced down the Ku Klux Klan, courage in Latin America, where they sprayed tear gas. She had courage in the bomb shelter in Hanoi. But the real courage came when she did this film entirely with natural light.’”

Baez needn’t worry. At 82, she is living proof that aging gracefully isn’t just a catch phrase. Her skin is preternaturally supple, her body lithe from dancing every chance she gets. In “I Am a Noise,” she also proves that honesty, even at its most uncomfortable, is far more compelling than just another celebrity swan song.

O’Connor and Navasky, who have made documentaries for the PBS series “Frontline” about mental health, prisons and aging, had discussed the possibility of making a film about Baez’s final concert tour for years, but what they first conceived as a conventional cinema verité chronicle morphed as circumstances changed and material emerged. “At one point, I was a big proponent of doing a film about Karen and Joan and their friendship,” recalls Navasky, who adds that since she and O’Connor usually make issue-driven documentaries, they also considered making the Baez material part of a larger series about aging and creativity.

O’Connor and Navasky started gathering material in 2013, catching an interview with Joan and Pauline at their mother’s 100th birthday party and, a few days later, capturing one of the most moving moments in “I Am a Noise,” when Joan Sr., nearing the end of her life, runs her hand lovingly through her daughter Joan’s silver hair. After that, O’Connor and Navasky returned to “Frontline,” where they made a film about transgender kids. In 2017, when Baez began seriously considering a final tour, the team began production in earnest.

O’Connor, Navasky and O’Boyle decided to go to California with families in tow and just “hunker down” for a month. The filmmakers began to delve into the enormous Baez family archive, which had accumulated over eight decades. “I knew her mom had saved stuff over the years, but I didn’t know the extent of it,” O’Connor recalls.

“You’d open a drawer and there was a letter about [hanging out with] the Beatles. And then there’s a letter from [Baez’s former husband] David Harris.” Baez made mention of a storage unit, but she had no idea what was in it. It turned out to be filled with tapes, drawings, answering machine messages, home movies, documents and memories. Baez gave O’Connor and her team the key, and then walked away.

Navasky and O’Boyle did the heavy lifting of organizing the materials into different timelines. It was Baez’s taped letters home during her first tours - often starting with “Hello, Mumsy, hello Popsy” - that “really cracked the movie open for me,” Navasky recalls. “We didn’t want it to be the 82-year-old looking back at her life,” O’Connor explains. “It would be capturing it there so that the past potentially could feel like the present. So that even in the past it would feel immediate and immersive.”

For her part, Baez intentionally kept her distance from the research phase, only occasionally leafing through letters that O’Connor would show her. “If I had been part of the process, it would have been impossible,” she says. “I would have wanted to censor everything.” She didn’t know what O’Connor and her team had unearthed “until the very end.”

The result is a densely layered, almost dreamlike film, in which the teenage Baez is vaulted to instant stardom, grapples with paralyzing anxiety and panic attacks, embarks on a famous romantic and artistic partnership with Bob Dylan, becomes involved in the civil rights movement, and struggles to find her footing when politics and musical tastes change in the 1980s and 1990s. “I Am a Noise” isn’t a comprehensive biopic - there’s no mention of Baez’s close relationship with Steve Jobs, for example, or her extensive human rights advocacy in Latin America and Sarajevo, Bosnia. Instead - and here, people who haven’t seen “I Am a Noise” might want to stop reading - the film focuses on her inner life, including recovered memories of alleged abuse by her father, Albert, that only surfaced in therapy when she was 50, and which caused deep conflicts within the Baez family.

O’Connor had been aware of those allegations for several years before she began making “I Am a Noise” (“It was not public, but it was known within Joan’s world,” she says). Because she knew the family so well, she explains, “I also knew there were conflicting stories about what had happened - her parents and Pauline had all denied the accusations. So the real challenge was to find a way to include the family’s voices and views while still allowing Joan to tell her own story.” Baez’s mother and father had died by the time the team did most of their filming, so the filmmakers used their taped and written letters to make sure their points of view were included.

“I’m happy that it’s even-handed,” Baez says. “One thing I always stress is that my parents didn’t remember this stuff. It’s hard for people to grasp that, but it makes all the difference. . . . The way I look at it is, it took me 50 years to get up the nerve to go and look, and that’s the last thing they wanted to do. That’s how I feel [that] it’s represented in the film, that they get their say.” - Inevitably, some viewers have quibbled about the recovered memories and other psychological material in “I Am a Noise” (Baez also candidly discusses her experience with multiple personality disorder, a controversial diagnosis). Call it the “Play the hits” syndrome; when you become an icon as venerated as Joan Baez, fans will always recoil when you have the nerve to chip away at the edifice. “There were panicked moments,” recalls Navasky. “Karen is very close to the people who are very close to Joan. [She was asking], ‘Is this going to feel bad for her family?’ We were constantly checking in with Joan, [asking her], ‘Do you really want to do this?’”

O’Connor remembers those conversations vividly. “We’ll do it with as much taste and intelligence as we can,” she recalls telling Baez, “but the fact of the matter is, it will be out there in the world, and it will change your legacy - your family’s legacy.”

“It will be out there in the world, but first it will be in your bedroom and in your mom’s house and upstairs and in the pool,” Baez says wryly, adding that there were moments during filming when her patience wore thin. (Let’s just say there’s an entire outtake reel’s worth of shots of Joan Baez raising her middle finger to the camera.) Baez balked when the team wanted to film a voice lesson in San Francisco, not wanting to be seen sticking out her tongue and “making these horrible noises”; they wound up filming a session at her home, next to a piano under Baez’s portrait of Dylan, her dog Ginger howling in unison with her vocal exercises. “The dog covered for me,” Baez says.

Navasky credits O’Connor with being able to push back when Baez said no. After filming an event at the Emanuel AME Church in Charleston, S.C., the team - which didn’t include O’Connor that day - went to the beach, where Baez wanted to go for a swim. “I said, ‘We need to film this,’” Navasky recalls. Cue the Baez middle finger as she dived into the ocean. “She just refused,” Navasky says. “If Karen was there, I’m sure we would have filmed it.”

As annoyed as Baez would occasionally get during the filming process, she has relatively few misgivings about “I Am a Noise.” Certain things in the film, she admits, are always hard to hear: her father leaving a heartfelt voice message; her son Gabe admitting how lonely he was as a child, when she was so often on the road; Pauline sharing how her sister’s growing fame led her to feel invisible. “To hear her say, ‘I just couldn’t do it, I just had to leave’ - oof,” Baez says. “There’s a lot of gut punches.”

At the outset, O’Connor insisted on final cut of the film; Baez had no power to make changes, although the filmmakers did agree to take out a scene of her having her makeup done before a CNN interview, because she usually does her own. Baez is more concerned that a sequence filmed in 2018, when she was suffering a mild panic attack, might lead people to think such episodes are still commonplace, when in reality “that doesn’t happen anymore.”

“You see that as less-than in your recovery and your health,” O’Connor says, turning toward Baez. “I think of it as life. Like, you can be much better and still have highs and lows. Life is beauty and sorrow.”

“Yeah,” Baez responds, “but it doesn’t get that low anymore.”

The sun is setting, and Baez and O’Connor are chatting as they’ve been doing for the past 37 years. (In a felicitous full circle, a snippet of that very first interview is included in “I Am a Noise”; look for Baez in a red necktie.)

O’Connor is talking about what an enormous trust fall Baez took in giving her and her team the key to her past. “It’s one thing to say you want to do the film but the kind of filmmaking we do is exhausting.” Then there are the emotional stakes. To quote Baez herself, why did O’Connor say yes? And would she do it again?

“Under the right circumstances and with the right subject,” she says, glancing over at Baez. “You were really ready. It’s not a tag line. You were ready to leave an honest legacy. And that changes everything.”