With his horn-rimmed glasses, boxy suits and wide grin, Paul Janeway would look more at home behind a bank counter than thrashing on stage like James Brown. And just two years ago, behind that counter is where you would have found him.

Now the former bank teller fronts St. Paul & the Broken Bones, the Alabama-based seven-piece rhythm-and-blues band that will close Spoleto Festival USA 2015 at the Wells Fargo Festival Finale, Sunday at Middleton Place.

“It’s been a heck of a year,” Janeway said of the time since the band released its full-length album, “Half the City,” in February 2014.

Fans and critics alike received the album’s soulful blues, punchy horns and vivacious vocals with overwhelming enthusiasm. David Letterman introduced the band’s performance of “Call Me,” which reached No. 62 on the Billboard Charts, by saying, “The first time I heard this song, I was screaming till I cried,” and then demanded an encore afterward.

And the Broken Bones recently earned some high-profile new fans when The Rolling Stones hired them as the opening act for two shows on their Zip Code tour this summer.

“It exceeded all of our expectations, and I think a lot of it is due to them working really hard,” said “Half the City” producer Ben Tanner, who also plays with fellow Southern R&B outfit Alabama Shakes.

Tanner worked with the Broken Bones to record “Half the City” in January 2013 on Single Lock Records. While they weren’t consciously trying to make a retro record, the soul of the band combined with understated sound editing to create an album that harks back to the days of smooth soul and Otis Redding.

“There’s not a lot of bells and whistles or tricks,” Tanner said. “It’s really just about capturing the energy and emotion of the moment. I think it’s refreshing for people to hear a record where it really is just people — real people — playing music.”

Janeway was raised on gospel and soul, which shines through in his passionate vocals and tireless onstage moving and shaking. He’s known for spilling his heart and soul into his shows. During a performance at the Coachella music festival in April, he performed so fervently that he slipped off the stage.

“I was just fine,” Janeway laughed. “More embarrassed than anything, really.”

The rest of the Broken Bones play with just as much enthusiasm, charm and grit as their patron saint, whipping up a frenzy of roots music sound and just plain fun.

Tanner said the Spoleto audience has a lot to look forward to.

“Their live show is electric and dynamic and really engaging,” he said. “Paul is an incredible singer, and it really gives people something to latch onto.”

St. Paul & the Broken Bones takes the stage at 8:30 p.m., but the finale festivities kick off rain or shine that afternoon at 3:30, when the gates and the Beer Garden open. Music starts soon after with performances by Johnny Delaware at 4:15 p.m. and Steve Fiori at 5:15 p.m.

“It’s going to be a lot of fun,” Janeway said. “We’re real excited to be coming.”

Kate Drozynski is a Goldring Arts Journalist from Syracuse University.