They call it bluegrass, but it comes in many shades. Gillian Welch’s interpretation of the genre usually comes in darker hues, with songs about death and addiction, sorrow and longing. But the tempo is often exultant, as Welch’s long-time partner Dave Rawlings livens the melody with fiery acoustic guitar picking.

During a song the duo recently performed at The Music Hall in Portsmouth, Rawlings played banjo and harmonica while Welch clapped and slapped her thighs for percussion, then hopped off the center-stage rug to clomp her boots on the bare floor in an impromptu barn dance. Her raw enjoyment beamed as she scampered back to the microphone, flashing Rawlings a wide, girlish smile in the process.

Still touring behind her fifth studio album, “The Harrow & The Harvest,” Welch played for a packed audience at The Music Hall on Saturday, Nov. 26. By now, Welch and Rawlings have become familiar faces on the Seacoast. The Dave Rawlings Machine, featuring Welch, played at The Music Hall in June 2010 and at the Hampton Beach Casino Ballroom in August 2009.

This time, though, Welch was at the helm, and she carried the crowd through a delectable menu of songs from her new album and throughout her career, alternating between slow, aching ballads and upbeat country hoedowns.

Fittingly, Welch opened the show with “Orphan Girl,” the opening track from her 1996 debut album “Revival.” The lyrical theme of forsaken loneliness is still prevalent in Welch’s music 15 years later. Over the course of the evening, she performed almost all of the 10 songs on “The Harrow & The Harvest.”

“This one’s kind of a downer,” she warned before playing “The Way It Will Be” early in the first set. “I lost you awhile ago / still I don’t know why / I can’t say your name / without a crow flying by,” she sang in a lush but woeful cowgirl croon.

Later, while introducing “My Morphine,” from her 1998 album “Hell Among the Yearlings,” Welch said it was a tune she rarely performed live. “It’s really kind of hard to fit all the slow, pitiful songs in,” she joked.

Welch is not one for sappy love songs; she’s more inclined to sing about a dying man’s tragic love affair with morphine, complete with mournful yodeling that seems to amplify the protagonist’s inconsolable desolation. Yet she has a way of celebrating the intrinsic beauty of life’s most heartrending struggles, lending an angelic voice to our inevitable pain. That quality seared through her chilling live rendition of “Elvis Presley Blues” and her achingly gorgeous performance of “Look at Miss Ohio,” the opening track of her 2003 record “Soul Journey.”

Welch’s robust vocals benefit from the constant garnishing of Rawlings’ dazzling instrumental work. He plays a vintage 1935 guitar, aiming the neck away from his body and rapidly jostling the strings, as if struggling to control a fire hose. He wore a slim-fitting gray suit, black boots and a Stetson hat that rattled on his head during particularly vigorous improvisations. He’s one of the best bluegrass guitarists on the circuit, and his solos often met with enthusiastic mid-song applause.

Rawlings snuck in a couple of songs from his 2009 album, “A Friend of a Friend,” including the lively folk number “Sweet Tooth”—a clear crowd favorite—and the record’s opening track “Ruby,” which he squeezed between a pair of Welch’s songs during the first of two encores.

Welch, meanwhile, wore a black sundress with brown cowboy boots, her blaze of red hair covering her eyes as she hunched over her guitar. She and Rawlings have settled into a symbiotic chemistry, singing and playing together with natural ease. They indulged in occasional jokes that kept the atmosphere light, commenting on their unusually large water glasses and offering anecdotes from their recent tour of Europe. When a crowd member obnoxiously requested “Free Bird,” Rawlings took it in stride.

“Still funny after all these years,” he said dubiously.

“But now for different reasons,” Welch added.

After two 45-minute sets, the duo reappeared for a three-song encore, starting with “Everything Is Free” and concluding with “I’ll Fly Away,” the song Welch famously performed on the soundtrack to “O Brother, Where Art Thou” in 2000.

But the crowd, still craving more, beckoned the pair back to the stage yet again with a standing, stomping ovation. This time, they started with “The Way the Whole Thing Ends,” the darkly absorbing closer from “The Harrow & The Harvest.”

“That’s the way the cornbread crumbles / That’s the way the whole thing ends,” Welch sang.

The final song came as a surprise to the audience, which had been fed a steady diet of folk, country and bluegrass fare. Beginning with a flourish of Latin-sounding guitar notes from Rawlings, the duo broke into an acoustic rendition of Jefferson Airplane’s psychedelic classic “White Rabbit.”

The crowd left sated from the post-Thanksgiving performance, reverberations of the dark yet illuminating tunes still twanging off the theater dome.