Tighten your pants until your voice changes. Take a hit of helium mixed with gravel. Close your eyes, rock back and whoop it out.

"Sshhhhaaaa-aaaa-aaaa-aaaa-aaaa-aaaa rrrrrreeeeeeee Bayyyyy- aaa-beeeeeeee"

"SHERRY BABY."

In 1962, that banshee falsetto cut through the air and a lot of teen-agers had to do quick checks on their car radios. Sounded like an air raid siren being tested. Couldn't believe their ears.

That falsetto was a beginning for the Four Seasons. Not the beginning, though only the cultists and Ed Sullivan would remember a 1956 false start with "You're the Apple of My Eye" by the Four Lovers. Sullivan had had those Lovers on, but the pride of the Newark, N.J., lounge circuit sank quicker than attempts to spell the lead singer's name blindfolded.

"There was an awful lot of early influence from R&B vocal groups who were doing a softer kind of falsetto," says the lead singer, who was Frank Castelluccio then and is Frankie Valli now. He speaks very softly, holds himself like a man who sold a lot of records. Did, too: 100 million at least, probably more. "Falsetto's always been a very important part of music as far back as I can remember.

"I never really thought about making it as a rock 'n' roll singer," Valli adds, and in fact, he hardly looks like someone who has made it as a rock 'n' roll singer. He's small and taut. The face is care-worn, the hair perfectly styled. At 46, dapper and direct, he could just as well be a successful accountant or dentist or barber. Instead, he sings.

"I was more interested in jazz," Valli confesses, "and I was involved in a group that did a lot of modern harmony, patterned itself very much after the Four Freshmen. I had the highest voice in the group and the falsetto was being used even in those times. I also did a lot impressions--Dinah Washington, Rose Murphy, a lot of blues singers.

"That's how I learned about the music business. My education came from buying records, taking them home, listening to them, analyzing what singers were doing, and practicing. I came from a poor family and there was no one to send me to school to learn about music. Especially my father, who was telling me every day that I should get a real job. I went through that for sooo long."

The redeeming image that kept going through Valli's mind had been implanted early at New York's fabled Paramount Theater by another undersized Italian-American singer.

"I remember seeing Frank Sinatra there when I was a kid. Looking up, I was amazed--I saw all these lights and all these women were fainting. It was a dream, but who the hell ever thought it would come true?"

Before it did, though, there would be a lot of lounges, a lot of names: the Varietones. Billy Dixon and the Topics. Hal Miller and the Rays. Frank Vally and the Romans. The group auditioned at a big suburban bowling alley once. "Didn't get the job but we lifted the name of the cocktail lounge." The Four Seasons.

By 1962, when they went into the recording studio one more time than a string of nowhere singles should have allowed, the Four Seasons already looked like an oldies group. Between takes, Valli jokingly fooled around with his falsetto. New member Bob Gaudio, one-time Royal Teen and composer of the classic "Short Shorts," suffered 15 minutes of inspiration in a back room and came back with "Sherry."

"Gaudio came in to the rehearsal, said 'Listen to this,' " Valli remembers. "His feeling was that we should take advantage of creating a sound that became us, so much so that if someone turned the radio on and heard the record, they'd say 'That's the Four Seasons.' And that's what the whole basic thing is all about. Those early records were really to establish our sound: they're street-oriented kind of records, ghetto talk, just basically that. As time went by we got a little bit more sophisticated."

All Valli knew about "Sherry" at the time was, "It was either going to be a smash or nothing at all because it was that different." He wasn't looking forward to another name change, so the relief was as huge as it was sudden. The Four Seasons appeared on Dick Clark's American Bandstand and the next day 150,000 copies of the song were sold.

"It was terrific. I don't think I really realized the impact of success until a couple of years went by. We kept knocking ourselves out of the No. 1 spot" with songs like "Big Girls Don't Cry," "Walk Like a Man," "Candy Girl," "Dawn (Go Away)," "Rag Doll," "Let's Hang On," "Oh What a Night!" In all, there were 39 Top 40 hits for Frankie Valli or the Four Seasons. The first group split occurred in 1967 but they've pursued parallel careers ever since, sometimes meeting over a hit single, sometimes touring together (though none of the original Seasons are still around). It's the sheer weight of past hits that allows Valli to headline tonight's "Loving Feelings" concert at the Capital Centre with The Supremes, the Four Tops, the Righteous Brothers and The Association.

The Four Seasons' first 80 million records were sold between 1962 and 1966, which is why one attaches words likes oldies and nostalgia to their appearance, and why they continue to play the revival circuit and the big resort lounges. Valli, whose last big hit was the No. 1 "Grease" in 1978, has had an up-and-down solo career. He has battled a serious hearing problem. He has lived well off the past. Early on, Valli made a shrewd move by buying back the master copies of his recordings. Since then, he's always controlled his music, leasing it out carefully. There is talk now about re-pressing albums with their original artwork for the cultists and collectors.

He and Bob Gaudio own a recording studio in Los Angeles and there is also talk of new deals, but no exasperation at the slowness of record companies to cut a deal. Valli thrives on the past, even on the bad memories. "In those early days, we were hardly ever with a major record company. When they told us we sold 2 million records, we knew it had to be four. Hey, that's what happened in those days."

It was a time when the tiny Vee-Jay company had signed both the Four Seasons and the just-becoming-known Beatles. The company capitalized by putting out a double album, "The Four Seasons versus the Beatles--International Battle of the Century!!!" (Says Valli: "There was a chart on the back where you actually scored it.")

It was a time of star caravans, playing the Brooklyn Fox with 13 acts, playing the Apollo in Harlem. In the early days, "Many people thought we were black. I did tours where we were the only white act on the show. There was more camaraderie then--you got to know and love each other. I made some really great friends in the early days. You'd ride and live and eat and sleep on the bus. I miss that, it was fun. If one of the acts wasn't feeling well, the acts on either side would fill in, do a bit longer to make up for it.

"I miss all the radio personalities--the Alan Freeds, the Murray the Ks, the Bruce Morrows, the Good Guys. It was terrific; radio and performer were like family. You came into a town and you visited every station and it was wonderful. Today, performers make 50 times the kind of money we made in those days and they won't go to a radio station, they take on an attitude that I can't quite understand."

Valli is comfortable. He even hints that all this success isn't necessary, that if "Sherry" had slipped by like everything before it, if there had been no million-sellers, if he'd never left the lounge circuit, that would have been all right, too.

"If I were successful working in Jersey lounges and making a good living at it, that's a success as much as the other way. I enjoyed a lot of what I did in those days. I think back sometimes how nice it would be to work in a lounge where you didn't have to do a set show and you did what you felt like doing."

On the other hand, there was the 100-million-record kind of success, which is okay by Frankie Valli, too. "What's good then is good always. That's how I always looked at it. Nostalgia is forever."