On Ash Wednesday the mood was far from somber in the Town Ballroom as a hearty crowd witnessed the progressive bluegrass band Punch Brothers perform an incomparable and unabashedly ecstatic set.

That the band is led by 31-year-old Chris Thile – the mandolin virtuoso who just received a 2012 “genius” grant from the MacArthur Foundation – made the evening all the more intriguing. The New York City-based quintet known as Punch Brothers originally formed in 2006 to play on Thile’s solo album “How To Grow a Woman From the Ground” and has steadily evolved from an elite gathering of individual musicians into a vibrant ensemble that darts to and from influences with both superior skill and reckless abandon. The music of Punch Brothers incorporates the informal aural traditions of folk, blues and rock, and the more formalized, often notated environments of classical and jazz scores – often within the same song.

Punch Brothers opened with its latest single, “Movement and Location.” The song’s rhythmic interplay is as intricate as the inner workings of the finest pocket watch: violinist Gabe Witcher’s rapid one-note repetition interlocked seamlessly with banjo player Noam Pikelny’s bouncing syncopation. Meanwhile, Thile’s engaging, agile tenor voice ascended into its sweet spot, an effortless falsetto as good as any in pop music.

The group followed with the shape-shifting song “Next to the Trash”: a verse of crooning country music brushes up against edgy, straight-ahead pop/rock before vaulting into a rousing waltz. The amped-up Western New Yorkers responded accordingly, prompting Thile to quip from the stage, “Maybe it’s not such a mellow Wednesday night after all.”

There was no turning back once the set arrived at “Who’s Feeling Young Now?” – which lays down a tasty groove and a grungy rock riff, capped by Witcher’s scorching solo that could only be described as heavy metal. A caffeinated cover of Jimmie Rodgers’ 1928 country song “Brakeman’s Blues” showcased not only Thile’s yodeling abilities but also awe-inspiring solos from each band member that challenged notions of an instrument’s perceived limitations.

Thile was positioned squarely in the center of the action, often joyfully conspiring with guitarist Chris Eldridge, or jaunting over to upright bassist Paul Kowert. You could easily tell how much Thile loved making music “in the moment,” embodied in every raise of the eyebrow or reminiscent wince, as in the haunting ballad “Missy.”

But for this concert, enthusiasm was a crowded two-way street. With earnestness, authenticity and playful charm, hearts were won over – and I’m talking about those belonging to the musicians. “This Girl,” about a Christian backslider who petitions his Heavenly Father for the girl of his dreams, morphed into a carefree sing-along. Thile momentarily fumbled the words to “Patchwork Girlfriend” when concertgoers’ full-throated background vocals pleasantly caught him off guard. The Town Ballroom crowd endeared itself to the Punch Brothers again and again, as demonstrated by the visibly thrilled frontman.

Among the best American bands working today, Punch Brothers combine all the speed and precision of bluegrass with trailblazing musical intuition. If you weren’t aware of the phenomenon before, Wednesday’s concert seared it into your memory. And if Thile and company weren’t quite aware how Buffalo audiences gear up for a show, they certainly know now.

Singer-songwriter Anais Mitchell and guitarist Jefferson Hamer opened the concert with a brief but well-polished set of folk songs in support of their forthcoming album “Child Ballads.”

However, Mitchell’s musical gifts seemed ill-suited here, alongside Punch Brothers’ more boisterous and experimental take on folk music traditions.