Oh, what a life

With that, Frankie Valli, known for his legendary falsetto with the Four Seasons, swings open the door.

A small man with neatly slicked-back silver hair, Valli looks sharp in creased khaki slacks, a khaki V-neck sweater with white T-shirt underneath, and a tasteful gold necklace. He’s all business as he takes a seat in the living room, the faint scent of cologne wafting through the room. He crosses his legs and stares as if to ask, “What the hell do you want?’’

The singer from the housing projects of Newark hasn’t lost his swagger, even in his 70s. (His age is the subject of much speculation, mostly because in the 1960s he altered the dates on record liner notes to appear younger. And no, he doesn’t want to talk about it.)

He is serious, with little patience for the irritations fame can bring, including reporters. But he also exudes a sincerity that may stem from his humble beginnings on the tough streets of New Jersey, where as a young man he tried to escape poverty and avoid any kind of serious trouble with the mob.

“I don’t like it here much,’’ he says immediately of Las Vegas, cracking a mischievous half smile. “I don’t know how anyone could live here. There’s no culture at all. I came up during the old days of Las Vegas. Now, that was great.’’

His distaste for Sin City aside, Valli is in town to see the Tony Award-winning musical “Jersey Boys: The Story of Frankie Valli and the Four Seasons.’’ The national tour comes to the Citi Shubert Theatre on Thursday.

“The cast was good,’’ he says, nodding. “I had no idea this show was going to be as successful as it is. No idea at all.’’

“Jersey Boys’’ became a box office smash after it hit Broadway in 2005, winning four Tonys, including the award for best musical. But real life for Valli and the rest of the Four Seasons came with its share of struggles, both on and off the stage. Chart-topping doo-wop hits were accompanied by brushes with the law, run-ins with wise guys, and serious debts. And until “Jersey Boys,’’ nobody knew their story.

“They were young kids - blue collar, Roman Catholic, Italian-American, first-generation high school dropouts who grew up in [expletive] little apartments in crappy neighborhoods outside of Newark, where on the living room walls there were two pictures, the Pope and Frank Sinatra,’’ explains “Jersey Boys’’ co-writer Rick Elice, who has also come to Las Vegas to see the show.

The idea for “Jersey Boys’’ was born during a casual lunch in 2002 among Valli, Elice, “Jersey Boys’’ co-writer Marshall Brickman (who helped write Woody Allen’s “Annie Hall’’ and “Manhattan Murder Mystery’’), and Bob Gaudio, Valli’s longtime songwriter and business partner.

“They started to describe what their early careers were like, and it was such a great story,’’ Elice says. “We were just sitting there with salad dressing dripping off our chins.’’

The Four Seasons’ hit “Sherry,’’ with that familiar falsetto, pours through loudspeakers in the lobby, rocketing an audience full of baby boomers back to 1962 and setting the mood for this toe-tapping crowd, which scrambles past Four Seasons memorabilia to reach the seats.

In a matter of moments, the audience is introduced to all the group’s original members: Gaudio, who sang in addition to writing songs; bass player and singer Nick Massi; lead guitarist Tommy DeVito, portrayed as the most troubled member of the band, with mob ties; and of course Valli. Spanning spring, summer, winter, and fall, (four seasons - clever!) and using such songs as “Can’t Take My Eyes Off You,’’ “Working My Way Back to You,’’ “Dawn,’’ and “My Eyes Adored You’’ as poignant markers to reflect moments in their lives, the show soon has audience members bopping, humming, and even wiping away tears as they follow the singers from poor neighborhoods to the Top 40, then into a long and painful downward spiral.

At the end, audience members stand for an ovation, some sniffling - and exit to purchase “Jersey Boys’’ CDs.

It isn’t easy for Valli to see his life unfold onstage, from the famous handshake with Gaudio that sealed their business partnership to the tragic death of his stepdaughter Celia in a 1980 car accident and, six months later, the fatal drug overdose of his daughter, Francine, a student - a wrenching moment portrayed in the show that still gives him pause.

“We decided early on that if we were gonna do this, tell the story of Frankie Valli and the Four Seasons, we were gonna have to tell the truth - the whole truth - or it isn’t our story,’’ Valli says.

He didn’t always feel that way. “In the early years we were scared to death someone would find out and record companies would drop us and radio stations wouldn’t play us,’’ Valli says. “Someone would find out all the things that occurred in our lives. I mean guys went to jail, and there were robberies, gambling, all this stuff.’’

That may seem mild compared to the kind of drug- and alcohol-fueled behavior that catapults today’s singers into infamy, rehab, and megastardom. Still, in those days Valli’s fear was real.

Born Francesco Castelluccio, Valli was the youngest of three children of Anthony, a display designer for model trains, and Mary, a beer company employee.

“I come from a very poor background,’’ Valli says. “And my mother was the greatest. I don’t know anybody who could stretch a dollar the way she could.’’

Valli, who remembers boiling hot water on the stove for baths and watching bookies and mob guys running around through his window, became fascinated with making music early on, after his mother took him to see Frank Sinatra when he was just 6 years old.

Even then he knew singing was his only way out. “Nobody was sending me to college,’’ he snorts. “There were few options for kids in my neighborhood. And I wasn’t getting mobbed up or going off to the military. And I pride myself for never taking an unemployment check in my life. I knew I had to do for myself.’’

He began emulating singers he heard on the radio - Sinatra, Nat King Cole, Ray Charles, even a little Ella Fitzgerald.

Still, he was living too close to the mob life to be unaffected. One guy, a boss named Angelo “Gyp’’ DeCarlo, was like a father to him, he says. In his youth, Valli even knocked over a grocery store or two, and was arrested.

“It had a terrible effect on my mother,’’ he says. “I didn’t want that.’’

(Valli did join the Mafia much later - but only as an actor, in HBO’s “The Sopranos.’’)

He would hang out in clubs on the outskirts of Newark, asking band members performing that night to give him a shot onstage. Armed with his searing falsetto, Valli blew audiences away. By 1953 he scored his first recording contract and hooked up with Tommy DeVito, and together they formed several groups, including the Four Lovers.

It wasn’t until 1959 that an annoying neighborhood kid named Joe Pesci - yes, the same Pesci who went on to Hollywood fame with mob movies like “GoodFellas’’ and “Casino’’ - introduced Valli and DeVito to Gaudio, a musician and songwriter. With Massi, they created the Four Seasons and soon went on to chart three No. 1 hits: 1962’s “Sherry’’ and “Big Girls Don’t Cry,’’ followed by “Walk Like A Man’’ in 1963.

Valli says he and Gaudio, who collaborated closely, agreed to split all their career earnings 50/50 - their revenues from royalties, TV appearances, record sales, concert earnings - on a mere handshake. It’s a deal that has lasted more than 40 years and that they still adhere to today. “In Jersey there were no contracts,’’ Valli says. “Men shook hands. That handshake was worth more than any contract.’’

Women flocked by the dozen to group members at the height of their fame, feeding their copious appetites. Valli himself has been married and divorced three times.

But as soon as fame found them, problems started to set in. Massi grew tired of life on the road. He left the group in 1965, and he ended up living in the basement of his wife’s home. He died in 2000 in a nursing home.

They were also beset by money woes. By the late ’60s the group was in tremendous debt. Bills that DeVito promised to pay were never paid, and the group found itself indebted to gamblers.

“For a long time me and him didn’t even talk,’’ says Valli, referring to DeVito and his poor money management. “He didn’t want to hire a manager because we had to pay ’em. We had no PR person ’cause Tommy didn’t want to pay ’em. We were in a lot of trouble financially, and he created the financial burden. The attorney came and said we can file bankruptcy, but I didn’t want to.’’

Instead, in 1970 Tommy gave up his stake in the group, and it took four years for Valli to pay the debts off.

Throughout the late ’60s and ’70s,Valli took every imaginable job he could get his hands on.

“I was living on $350 a week and here I was - a star,’’ he says.

Meanwhile, Gaudio wasn’t a fan of the limelight. He was ambitious and wanted to work behind the scenes, writing songs and making music, so he too decided to stop touring with Valli in late 1971. Valli continued to perform with replacements, but he considers Gaudio’s departure the beginning of the end for the Four Seasons, which nevertheless continued to score hits like “December, 1963 (Oh, What a Night),’’ which Gaudio co-wrote, until the mid-70s.

Gaudio doesn’t regret his decision. He has worked with singers such as Diana Ross, Michael Jackson, and Barry Manilow and has produced six albums for Neil Diamond. As for DeVito, he lives in Las Vegas and works for Pesci, Valli says.

“Tommy could have been an incredibly talented guy and had all of these musical talents that he overlooked,’’ Valli says. “He had a thing about gangsters. He thought Al Capone was a genius. He loved to gamble. And Nick was a extraordinary talent - one of the most incredible vocal arrangers I’ve known in my life.’’

But with the original guys gone, Valli eventually went solo, and he’s still packing houses and releasing CDs to this day.

“We embarked on a rather lengthy process of getting them to trust us,’’ Elice says. “We had to earn the right to tell their story. And I think it was courageous, putting it all out there, warts and all.’’

Valli and Gaudio, being the smart businessmen that they are, own the rights to most of the material performed in the musical. They first saw the show in its debut at La Jolla Playhouse in California. Together they made some tweaks, and the rest is history.

Despite everything, Valli never forgot his former pals from the neighborhood.

“When ‘Jersey Boys’ was about to go into production, I went to Bob and I said, ‘We really have been blessed men. We are sound and healthy, and I wouldn’t feel right unless we give these guys a taste of ‘Jersey Boys,’ ’’ says Valli. “I mean, we created this thing together, and I was looking at these guys and they were destitute. Tommy was working for Pesci to make a few dollars, and Nick was living in the basement before he moved to a senior living facility and died. We gave them a percentage. I mean, it has always been about the group.’’

With that, Valli’s cellphone rang.

“Look, I gotta take this,’’ he says, and leaves the room.