One might suppose that at the heart of any relationship — especially a fruitful, artistic one that has lasted more than 30 years — some commonality, some mutual trait would be present.
Not so in the case of the Grammy-winning contemporary folk duo Indigo Girls. When Emily Saliers explains the secret to her long-running musical alliance with Amy Ray, little is revealed by way of an obvious, immediate common bond.
"We are the quintessential yin and yang," said Saliers, who returns to Lexington with Ray for an Indigo Girls performance Monday at the Kentucky Theatre. "We have always been diametrically opposed in terms of our sensibilities, our energy, in the ways we express ourselves, ... in everything, really.
"But the differences have made us hang together all these years — that plus the respect we have for each other as human beings."
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That's not to say the music that Saliers, 48, and Ray, 47, create hasn't bumped into a few shared passions, including intense political and social activism ("That is integral to everything we do," Saliers said). But the stylistic differences between the two artists, as singers and as writers, have fueled some of the Indigo Girls' finest music.
Take, for example, the duo's 14th and newest studio album, Beauty Queen Sister, out last month. Marked often by elegiac strings and roots-savvy strains of banjo and violin that provide the songs with a decidedly summery feel, the record shifts from Saliers' country-esque Gone to Ray's more electrified title tune.
Yet as the record heads into the home stretch with the electric folk gusto of Making Promises and the Celtic-charged Damo, the music's strength comes from the combined artistic profiles of the two — that and a level of artistic maturity drawn from a working partnership that began when Saliers and Ray started singing together as high school students in Decatur, Ga. They formed the Indigo Girls while students at Emory University in Atlanta.
"Life experiences can definitely influence songwriting," Saliers said. "But I don't know if they broaden it or shrink it. What I do know is that Beauty Queen Sister is definitely a record we couldn't have written 20 years ago.
"Say you start out making records when you are in your mid-20s. You're sort of marked by what happens at that time. But if you're still making records 20 years later, you can't help but compare now to then. There is definitely a maturity at work.
"We wrote songs early on that we still love. But now I feel we don't put a song on a record unless we really love it and feel connected to it. I feel that through life, your connections naturally become deeper. So this is definitely a mature record that we've made."
Beauty Queen Sister also is an album of connections and reconnections. Returning as producer is Peter Collins, who has overseen recording sessions for such wildly disparate artists as Rush, Nanci Griffith, Queensryche, October Project and Alice Cooper.
Not coincidentally, Collins produced several of Indigo Girls' best-selling and best-received albums, including 1992's Rites of Passage, 1994's Swamp Ophelia and 2002's Become You.
"There is no doubt Peter was at the helm of this album," Saliers said. "He is a producer who believes nothing is superfluous, nothing is wasted. He is just a really musical guy. Yet even if Amy and I worked three months on a guitar part and he felt it was repetitive or was simply not working, it was, 'Scrap that.'
"And that can be a hard pill to swallow. But at this point in our lives, we are able to swallow it."
Recording sessions for Beauty Queen Sister also brought Saliers and Ray to the Britain-born producer's adopted hometown, Nashville. That allowed the participation of such esteemed artists as drummer Brady Blade ("He can play trashy, he can play funky, ... he's a genius"), bassist Viktor Krauss, violinist Luke Bulla and singer/songsmith Lucy Wainwright Roche, among others.
"Aside from working with Peter again, we got these wonderful players. These guys — I say 'guys,' but I mean men and women — played brilliantly. They really made the record what it is.
"We were making a record where the focus was on the songs. But the production and the players made those songs many times bigger and better than they ever could have been on their own."