DAVID Roberts is one banker you can cheer. Make that former banker. He has foregone working in Wall Street to concentrate full time on Straight No Chaser, the American a cappella group he first joined in his student days at Indiana University in Bloomington.

On Thursday, the reassembled group will play the Grand Opera House, York, as part of their first British tour.

“We started at university in 1996, but then we went our separate ways in 1999 to 2000 to do separate things,” says David, on the line from Chicago, Illinois, before flying to the UK.

“I got a masters in finance and worked for a bank in New York, and at the time, everyone was like, ‘Are you sure?’, as a bank job wasn’t exactly stable at that time.”

For the tenth anniversary of their formation, the original members of Straight No Chaser were invited back to the university where the a cappella group had continued by recruiting members as and when others left Bloomington.

The 2006 reunion show prompted founder Randy Stine to post clips from a 1998 concert on YouTube. “We then put our version of The 12 Days Of Christmas on there in 2007 and we had seven million hits in four weeks,” says David. “That surprised us!”

So did an email sent to Stine by Craig Kallman, chairman of Atlantic Records. So much so that Stine assumed it was a prank, but he and fellow founder Dan Ponce were whisked off to Los Angeles to meet Kallman, and a few days later the group convened in New York City to sign a record deal.

“He asked us if we’d consider making some recordings for Atlantic, and that’s what we then did in down-time or vacation time, when we went back to our old studio at our university to work with our sound engineering friend Dave Webber,” says David, recalling the gestation of their debut album of festive songs, Holiday Spirits.

“Atlantic threw enough money at us to cover the cost of travel expenses and recording, and though no one thought it would come to anything, we sold 100,000 records in the first three months, five times what the label expected.”

Initially, David combined his bank job with Straight No Chaser commitments, but something had to give. “I did both for a little more than a year, and it was exhausting,” he says. “I would work 60 to 70 hours a week and then travel at the weekend to perform. So I’m just starting to recover from that.”

David has concentrated on Straight No Chaser since August 2009. Album number two, Christmas Cheers, followed that winter, and the following year the ten-piece branched out into pop territory on With A Twist.

Collaborating with Christmas Cheers producer Deke Sheron on 12 tracks, they fused Jason Mraz’s I’m Yours with Israel Kamakawiwoole’s treatment of Over The Rainbow and brought their harmony skills to Gloria Jones/Soft Cell’s Tainted Love, Queen’s You’re My Best Friend, Coldplay’s Fix You and the Oasis busking staple, Wonderwall.

They have since released an EP, Six Pack, Vol. 2, revitalising Marvin Gaye’s Let’s Get It On and Weezer’s Buddy Holly the Straight No Chaser way, and “mashing up” Rhythm Of Love and Elvis’s Can’t Help Falling In Love.

Above all else, Straight No Chaser revel in the pleasure of unadorned singing. “I’d always enjoyed being part of a choir at high school, and at Indiana University all the original members of the group were in the choir there called The Singing Hoosiers, named after the university mascot. It’s a good way for freshmen to meet girls,” says David.

Now, Straight No Chaser are on a mission to change the image of male a cappella groups as “students in blue blazers, ties and khakis singing traditional college songs on ivied campuses”.

“That’s what we’re trying to do for sure. There’s the stereotype that it’s a dorky kind of thing to do; I don’t know why, but popularity always surrounds sports and there’s a little stigma around drama geeks and choir geeks,” says David.

“It’s fun trying to break people’s perceptions – and after they see us live the reaction is very different. We’re a bunch of friends having a good time on stage; keeping audiences on their toes with mash-ups of songs with similar chord progressions; making fun of ourselves; breaking down the fourth wall, acting like we’re still hanging out at college.”

British audiences at large have their first chance to watch Straight No Chaser at work this winter on their debut tour, but Katherine Jenkins fans may have encountered the group last year.

“We came over to promote With A Trust and did some spots with Katherine: we even did a show with her at the Royal Albert Hall, and we were pinching ourselves that we were doing that,” says David.

Last May, they opened for Barry Manilow at The 02 in London, another highlight that David could never have envisaged in his banking days.

“For somebody who used to sit in a cubicle for 70 hours a week to be playing some of the most beautiful and wonderful venues in the world has been an amazing experience,” he says.

Now he can add York’s Grand Opera House to that list.

• Straight No Chaser will play Grand Opera House, York, on Thursday, 7.30pm. Tickets update: still available on 0844 871 3024 or online at atgtickets.com/york