Emily Saliers was only 12 when Joan Baez’s Diamonds & Rust was released in 1975. And Saliers, half of the Indigo Girls folk-rock duo, listened to it nonstop. “I listened to the record over and over again until I could learn it,” Saliers tells EW over the phone from Canada. But her interest in Baez wasn’t just song-deep.

“I was very admiring of her politics and her journeys and the peace that she stood for,” she says.

Baez, in turn, remembers the Indigo Girls as the first of the “younger groups that I had open for me,” after her manager brought her to a concert in the early ’90s. “It gave me an opportunity to hang out with younger artists,” Baez says via telephone from her home outside Stanford, Calif. “It gave them an opportunity to be seen by a larger group.”

To sum it up in two clichés: It was the beginning of a beautiful friendship and the rest is history. That history — including several shared performances, a devotion to activism, children and grandchildren and secure spots in the folk pantheon — will culminate when the three musicians perform at the Cuthbert Amphitheater June 25.

“This time it’s just us,” Baez says. “They don’t have a band, which for me is the ultimate.”

“To stand on the same stage with her, I can’t believe it’s my life. I know it’s a cliché but it’s true,” Saliers says, laughing. “Then to have someone who’s that much of a legend who’s still completely true to her politics and her vision is quite remarkable.”

Over half a century has passed since a 22-year-old Baez performed “We Shall Overcome” at the March on Washington for 300,000 people — Martin Luther King Jr. recited the lyrics in his last sermon. At the end of 2012, she performed for an Occupy Wall Street rally. This spring, she toured Argentina, Chile, Uruguay and Brazil — 23 years after the Brazilian government banned her singing while on tour because of her human rights activism (“The police just came to the hotel room and handed me this paper saying that if you get anywhere near a microphone, we’ll arrest you,” Baez recalls).

This has not gone unnoticed by the Indigo Girls.

“I certainly learned that you can persevere through time and remain true to your vision,” Saliers says of Baez. “Some people talk about as some activists get older, they sort of mellow out and disappear. I don’t think Amy [Ray] and I are ever going to be like that. I think we’re going to stay true to what’s important to us in terms of causes and Joan is a prime example of not only continuing to … be an activist and support good causes, but also to continue performing into her 70s.”

Saliers and Ray, who both recently turned 50 and became mothers, are gearing up to record their 15th album in Atlanta, due out in early 2015. “It’s going to be pretty homegrown,” Saliers says. “A lot of people we’re working with are a lot younger.” The Indigo Girls are also embarking on a new project bringing music opportunities to underserved students in Georgia.

Baez laughs when I tell her of the Indigo Girls’ enduring admiration. “They are so smart,” she says. “Whenever we’re sitting and talking, they would know much more than I do about what’s going on in general,” she says.

And her thoughts on the state of activism today?

“The direction, it’s been kind of rudderless,” Baez says. “The feeling when Obama was running for president — that feeling hadn’t happened really in a big scale since King. That’s what I think is missing. People keep looking and hoping, ‘When is someone going to write “Imagine” again? When is someone going to write “Blowing in the Wind?”’ We have to reinvent our lives and whatever the social change is going to be.”

Joan Baez plays with the Indigo Girls 7:30 pm Wednesday, June 25, at the Cuthbert Amphitheater; $32.50-$55.