Twelve-time Grammy Award winner Emmylou Harris, right, performs at Wolf Trap National Park during her tour with John Prine. (Kyle Gustafson/For The Washington Post)

Emmylou Harris has been covering Kitty Wells’s “Making Believe” for decades. When she played the melancholy ballad at Wolf Trap on Wednesday night, it was one country legend’s tribute to another: Wells, 92, died in July. Introducing the song, Harris said she’d begun singing country songs “ironically” during her long-ago days as a folkie.

Youthful insouciance aside, there wasn’t a molecule of too-cool-for-school remove in Harris’s performance. Leading a shambling five-piece ensemble known as the Red Dirt Boys, Harris wove a set as representative of her 40-something-year career as could be imagined in 90 minutes. Among classics from the songbook of her seminal partner Gram Parsons (“Wheels,” “Luxury Liner”) and contemporary masters like Gillian Welch (“Orphan Girl”), Harris showcased her own late-blooming gifts as a songwriter. Of four songs from her most recent album, last year’s “Hard Bargain,” the most arresting was “My Name Is Emmet Till,” about the 14-year-old victim of a racially motivated killing in Mississippi in 1955.

For a woman whose songs often explore decline and death, the 65-year-old Harris sounded remarkably youthful, her silvery pipes betraying no sign of mileage.

Harris co-headlined the show with her contemporary John Prine. His 90 minutes were occasionally as somber as hers but funnier, too: Flanked by a second guitarist and a bass player, Prine performed stripped-down trio arrangements of “Picture Show,” “Fish and Whistle” and other instantly tuneful, novelty-skirting songs for a crowd that was uncommonly boisterous, by the inside-voice standards of Wolf Trap, in their appreciation. Harris joined him onstage for three numbers, none more enjoyable than the mildly ribald “In Spite of Ourselves.” Harris had to read its suggestive verses from a lyric sheet, but she was grinning ear to ear as she sang.

Klimek is a freelance writer.