When it comes to harmonizing duos, it doesn’t get much better than Gillian Welch and her partner, guitarist David Rawlings. Welch was adopted by musicians who worked as writers for “The Carol Burnett Show” in Los Angeles (her biological mother may have been raised in the mountains of North Carolina) and she later played in goth and psychedelic bands while a photography student at the University of California at Santa Cruz. But her musical heart soon fixed on old-school bluegrass, folk and Americana, leading her to meet Rawlings at the Berklee College of Music in Boston, where they formed a duo before settling in Nashville. Since then, they’ve become a universally acclaimed, Grammy-nominated duo whose delicate, sparse style and evocative lyrics combine for a beguiling new Southern sound, at turns dark and achingly beautiful. In concert they always cast a mesmerizing spell, which should only be enhanced by the Maymont setting. The show is Sunday, Aug. 21, at 8 p.m. musicatmaymont.com.