By day, Brian Duprey is a 33-year-old guy who can sing. But at night, he slips on a tuxedo and summons up the swagger necessary to become Frank Sinatra, Ol' Blue Eyes, leader of the Rat Pack.

"I'm kind of like Superman, like Clark Kent: You don't know what he does when you see him during the day," Duprey said in a phone interview. "Being Sinatra, there are no ramifications for what you say or what you do. He was the Chairman of the Board; he wasn't afraid to say whatever came out of his mouth."

Duprey, along with Tom Wallek as Joey Bishop, Johnny Edwards as Dean Martin and Kenny Jones as Sammy Davis Jr., will bring a Vegas vibe to the Rushmore Plaza Civic Center theater this weekend. Their show, "The Rat Pack is Back," is part of the Broadway Play Series - and it just may have audiences snapping their fingers and itching to stir up a martini.

"We try to recreate a typical show if you were taken back in time to the Sands' Copa Room," said Duprey. "We update some things, such as the jokes, and we stay true to the songs because we don't want to cheat the audience."

Back in time would be the early 1960s, when Sinatra and his pals were filming "Ocean's Eleven" in Las Vegas. At night, Sinatra would perform at The Sands Hotel, often joined onstage - spontaneously, it seemed - by Martin, Davis and Bishop. Audiences flocked to the shows, never knowing who might show up to perform. They were dubbed the Rat Pack, although Sinatra called his group of friends the Summit or the Clan.

The "Rat Pack" reprise will feature onstage banter, jokes and signature songs from the '60s and beyond, including Martin's "That's Amore," Davis' "Mr. Bojangles" and Sinatra's "My Way" and "Fly Me to the Moon," all backed up by a rhythm section, horns and piano.

Are the cocktail quips scripted, or do the performers take an improvisational cue from the real Rat Packers?

"We have a loose script, depending on what happens with the audience," said Duprey. "No night is the same."

But don't expect Duprey's Sinatra to be a carbon copy of the real thing. From his bobby-soxer fame to his Oscar for "From Here to Eternity," his affair with Ava Gardner and his decades of hits - including "Strangers in the Night," "It Was a Very Good Year" and "New York, New York" - there could be only one Sinatra.

"I consider this a light form of acting. I'm playing Sinatra in the 1960s when he was with his pals on stage. I do it in a way that doesn't seem forced or contrived. I try to stay away from a caricature and try to be more of a natural," he said.

Duprey has been with the show since 2005, but has been a Sinatra fan since he was about 14. "I just discovered him on my own," he said. "I've always been connected to that type of music."

He also was drawn to Sinatra's voice. "I've always liked baritone voices - probably because I always had a deeper, resonant voice," he said.

Duprey was in the corporate world before making music his career, and sang just for fun.

"I worked for several different companies, and started taking voice lessons in New York City. My buddies encouraged me to audition for a talent show on a cruise ship, and I made it to the finals and sang in front of a big audience. That's the only way that I feel like I'm doing something unique. The only time I ever felt empowered was when I was on stage," he said.

Playing the popular crooner has given Duprey plenty of stage time. After the show, Duprey said the performers like to mingle with audience members, who have been responding to the music and the era.

"I think there's a definite desire and need for this type of music," said Duprey. "In today's market, you can buy a CD and see (a group) perform live, but here, we can't. This is our way of letting them see this music live."

Contact Deanna Darr at 394-8416 or deanna.darr@rapidcityjournal.com.

If you go

What: "The Rat Pack is Back," part of the Broadway Play Series

When: 7:30 p.m. today, Sept. 26, 2 p.m. and 7:30 p.m. Saturday, Sept. 27

Admission: By season ticket or individually, $48-$58; tickets available at the civic center box office, 394-4111, 1-800-GOT-MINE or www.gotmine.com.