The singer-songwriter tradition is immune to age. Even protest songs, so often connected to a specific movement or historical event, continue to resonate decades later, such as Bob Dylan's withering "Masters of War" or Neil Young's outraged "Ohio."
"It's like old, old folk music that just lasts through time, like Woody Guthrie," says Emily Saliers of the Indigo Girls, who will perform Saturday at the Sun Theatre in Anaheim. "I think you pick up on the intensity of the message and the importance of what was going on then."
For the Indigo Girls, songs of social-political content have always mixed easily with more personal material, following a precedent set by an earlier generation of folk-based performers. As a young fan, Saliers first learned of alarming events in Central America at a Jackson Browne concert in the early '80s.
The Indigo duo began playing about the same time, emerging during a modern folk revival led by Tracy Chapman and Suzanne Vega, and scoring an early college radio hit with the emotional "Closer to Fine." Now they regularly trade political e-mails with singer-activist Bonnie Raitt, and feminist author Susan Faludi recently wrote liner notes for the band, placing the Indigo Girls in musical and political context.
At their shows, the Indigo Girls provide space for activist groups to distribute information on various causes, from women's and gay rights to battles against AIDS and the death penalty. Contact information for those same groups is usually printed on the band's albums.
"I don't think we can separate it from ourselves," says Saliers, 38. "No matter what we did for a living, we'd both be activists just because there's so much work to be done.
"We do find that a lot of mainstream artists that we ask to do political things are very wary of it. I think they underestimate what people might become interested in, if only they were exposed to it."
The Atlanta pair's current monthlong tour spotlights new material slated for its next album. At the Sun Theatre, Saliers and partner Amy Ray, also 38, will perform alone, accompanied only by their guitars and occasional mandolin and banjo, which is a shift in direction from their last album, 1999's more rocking "Come On Now Social."
"We were sort of moving in that direction, but Amy's been wanting to step into more of an acoustic direction," says Saliers. "That's what we are going to do this time, which is have the ensemble sitting around in a circle and cutting the songs live. No electric guitars and no samples."
So far, the new songs have taken a more personal direction, including some with an Appalachian flair. One explores spirituality, inspired by the recent death of Saliers' sister. Another examines "the complexities of relationships and the stuff that you don't learn until you're past 30."
"I'm sure we'll squeak a couple of political numbers in there before it's all said and done," Saliers says.
The songs are the first new material from the Indigo Girls since a pair of songs added to last year's "Retrospective." But earlier this year, Ray released the first solo album to emerge from the duo and was notably harder-edged than most Indigo Girls recordings. The album was called "Stag" and released on Ray's own Daemon Records label.
"When it first came out and the reviews were really good, I was like: 'Oh, my God, I feel a little insecure,"' Saliers says now with a laugh. "And I had to go through some of that. I wrestled with it for a while and then I got over it. It was just an adjustment period and now it's great."
As a result of "Stag," Saliers adds, more rock-oriented fans have been drawn to Indigo Girls shows, cheering whenever that album is mentioned. Saliers now has plans for her own solo record, most likely leaning more toward pop and R&B.;
On the duo's tour, each of the singers spends a few minutes alone onstage. Ray performs two solo songs, "Lucy Stoners" and "Johnny Rottentail," while Saliers sings "Philosophy of Loss," a hidden track on the last album focused on gay rights.
"I think it's good for us as Indigo Girls," Saliers says. "We look at the whole solo thing philosophically. If you set up a model of a relationship, what helps each individual grow will help the group, ultimately. It just brings more interest and more experience and more self-fulfillment."
Indigo Girls, with Michelle Malone and Peeps Show, play Saturday at the Sun Theatre, 2200 E. Katella Ave., Anaheim. 8 p.m. $20 to $40. (714) 712-2700.