The persistence of the human spirit is a big theme for one two-hour play.

But Glade Spring family physician and mountain-music afficionado Douglas Pote makes it go down as smoothly as cornbread and milk in “Man of Constant Sorrow: The Story of the Stanley Brothers.”

Pote wrote the play as a followup to his popular “Keep on the Sunny Side: The Songs and Story of the Original Carter Family.” That show traveled to 23 states and did a stint at Roanoke’s Mill Mountain Theatre in 2002.

A collaboration between Mill Mountain and Abingdon’s Barter Theatre, “Man of Constant Sorrow” had gray-hairs in Thursday’s preview audience whoopin’ and hollerin’ by the end of the show’s first number, “How Mountain Girls Can Love.” A few ladies in the audience looked like they might faint as actors Nicholas Piper and Gill Braswell impersonated Carter and Ralph Stanley.

It was as if Elvis were in the building.

While music serves as the draw, it’s the show’s ideas that will keep audiences pondering “Man of Constant Sorrow” for weeks.

Directed by Derek Davidson, the show plugs away at the mystery that drives artists to create. Why do they press on long after it’s obvious they will never earn riches or fame?

What pushed Ralph and Carter to drive all night to a gig four states away? Why did they continue with their old-fashioned music when few seemed to appreciate it and when it meant leaving behind their loved ones and mountain home?

Carter, Pote muses, did it to drive out his demons. Ralph sings about things he loves because singing makes him happy. Smartly, Pote hinged the drama on the two very different siblings: the outwardly gregarious but internally sorrowful Carter and the eternally grateful, sometimes stubborn Ralph. Folks new to bluegrass will get a powerful introduction to Carter, the awe-inspiring figure whom they may never have heard of before.

Piper as Carter and Braswell as Ralph, accompanied by phenomenal musicians Buddy Woodward, Ed Snodderly and Brandon Story as the Clinch Mountain Boys, sang with open hearts Thursday, dishing out bluegrass as good as you’ll hear anywhere in the mountains. Like Carter and Ralph, Piper and Braswell complement each other’s distinctive voices to create an unforgettable sound that’s more powerful than they could achieve alone.

Braswell is blessed with a pitch-perfect sense of humor. His collection of facial expressions ought to be put on display in the Smithsonian. Piper made a more somber impression as Carter. His portrayal of a man at ease with a guitar but floundering painfully through life is one of the most dynamic performances I’ve seen at Mill Mountain.

By the time the performers came out to take a bow Thursday, the crowd had gone nutty, clapping so hard during a standing ovation their hands must have hurt. It’s too bad the cast didn’t capitalize on the audience’s fever. Everyone hungered for an encore. A reprise of “I’ll Fly Away” would have put the perfect exclamation point on a pretty perfect night.