Not every music festival tries to change the world one song at a time. But that’s been the mission of Clearwater’s Great Hudson River Revival, also known as the annual Clearwater festival, ever since folk icon Pete Seeger founded it in the 1960s.

Back then, Seeger held a series of small concerts that raised money to build a sloop, an old-fashioned sailboat that would inspire locals to help clean up the heavily polluted Hudson River. And although the festival has evolved into a two-day outdoor event — with a lineup of more than 100 acts that will perform across seven stages at Croton Point Park on Saturday and Sunday — it hasn’t lost its grassroots flavor.

Now, the festival is manned by more than 1,100 volunteers, with an “activist area” to support a variety of causes and riverfront activities promoting environmental advocacy. Proceeds go to Hudson River Sloop Clearwater, a nonprofit dedicated to protecting the river that holds educational programs serving more than 15,000 students and 200 teachers each year.

“I don’t know if I can think of one other person who’s had more of an impact on the environment in this area than Pete Seeger,” says Steve Lurie, the festival’s director.

Music, however, is what powers Clearwater — and the uninitiated shouldn’t think it’s only for aging hippies hoping to reclaim their Woodstock-loving youth. Among this year’s performers are veterans Kris Kristofferson, Judy Collins, David Bromberg and Hot Tuna, but there also are plenty of fresh up-and-comers like singer-songwriters Nicole Atkins and Martha Redbone.

“This is like a dream come true for me,” says Redbone, a Native American indie artist making her Clearwater debut. “This is going to be a magical weekend.”

Redbone says she was “turning cartwheels” after receiving an invitation to play the festival, and not just because she’ll be among musical figures she’s long admired like folk-rock legend Buffy Sainte-Marie. She also feels privileged to take part in an event that continues Seeger’s hope that singing together can inspire change.“I think he’s an example for us all really in every possible way,” says Redbone of Seeger. “Instead of reaping accolades, he’s turned to communities to have them help themselves.”

Part of Seeger’s vision, too, is to offer racially diverse performers from a variety of genres. So this year’s concertgoers will enjoy appearances by: Antibalas, an Afrobeat band; Delhi 2 Dublin, a fusion of Bhangra and Celtic music; and Malian singer Boureima “Vieux” Farka Touré.

There also will be some interesting collaborations, such as the highly anticipated one between Seeger, 94, and longtime friend Lorre Wyatt. And solo artist Keller Williams has played the festival before, but this time around, he’ll pair up with bluegrass group the Travelin’ McCourys.

Though the Clearwater atmosphere is laid back, Williams says that the vibe is different from other festivals: folks who attend are true music lovers who really listen to the performers.

“It’s refreshing, yet nerve-wracking, in a good way,” he says.

And lots of those audience members will be children. The festival takes pride in being a family-friendly affair, where parents and kids can get out on the water: You can sail on the sloop Clearwater and the schooner Mystic Whaler, as well as take a ride in a small boat, canoe or kayak. Educational exhibits give information about the Hudson and the creatures that live in it, and other activities include face painting, a petting zoo and an instrument building workshop.

“We have tons of families that come in three generations,” says Lurie.