When the Indigo Girls get into one of their folk-driven tunes, there are moments where Amy Ray's stormy alto and Emily Saliers' warm soprano answer each other in impossible rhythms like a somniloquent conversation between lifemates. On their latest release, "Shaming of the Sun," due in stores Tuesday, the 14-year-old duo creates an exhilirating exchange of opposites with every note.

"Shaming" represents the Girls' first attempt at co-production, and their ambition pays off. From the quickpicking banjo thrill of the opening track, "Shame On You," to the wistful road-trip goodbyes of "Hey Kind Friend," Saliers and Ray have never been so complex or consistent in their vision.

Saliers' tender aspects shine through in the elegiac piano on "Leeds," whose lyrics touch on last year's church burnings in the midwest. "Everything Has Its Own Time" is blessed by its wisdom and heartbreaking melodies, swelled by military drums, harmonium and mandolin. Ray's works are more primal but no less immediate, as with the tribal "Shed Your Skin" and "Scooter Boys," a stark rumination on colonization: "They said we're stealing from the best to feed the poor," Ray growls. "Well, they need more."

Guest appearances by Steve Earle, Lisa Germano and Smoke transform "Shaming" into a kind of kindred reunion. Native American singers Ulali bring their chilling vocals to a few tracks, and Ani DiFranco drummer Andy Stochansky lends his cadences to others. "Shaming" is as satisfying as a summer feast, alive with flavor and goodness. It's a perfect soundtrack for the months to come.

-- Beth Winegarner

This article was originally published in the San Francisco Chronicle.