‘I Love My Wife’ at Brentwood Theatre

If Masters and Johnson had been a musical writing team instead of sex researchers regularly appearing on TV talk shows, they might very well have come up with something similar to “I Love My Wife.” The 1977 musical, about two guys from Trenton, N.J., who want to spice up their marital beds by swapping partners for a night, tries to push the erotic envelope -- but not so much that it will offend the Mike Douglas-Merv Griffin set.

Jason Alexander and Patrick Cassidy look like they’re having a ball playing Alvin and Wally, the beer buddies who are determined to put a little kink into their suburban routines. But the fun of this Reprise Theatre Company offering, now at the Brentwood Theatre under Larry Moss’ wobbly direction, is infectious only to a point.

The show ran for more than two years on Broadway but has largely faded from memory. Trivial Pursuit champs, of course, will be able to tell you that “I Love My Wife” opened around the same time as “Annie,” though unlike the unstoppable redhead, it hasn’t had an impressive afterlife.

Reprise has long made it its business to retrieve musicals from the dinner-theater dust heap, but the only place this one should be headed to is the time capsule -- as an example of the mediocre art generated by the tirelessly self-referential “Me Generation.” Suffice it to say, you know a show is dated beyond redemption when its farcical plot is set in motion by a sex quiz in a women’s magazine.

Michael Stewart’s book still has a few bubbles left, but the soda is undeniably flat. Compared to the great television comedies of its era, the show’s broad sitcom high jinks squeeze out the possibility of compelling character moments. The novelty of “swinging” can no longer mask the work’s ham-fisted construction. And when Cy Coleman’s jazzy (though second-drawer for him) score isn’t being performed, the musical is a real chore to sit through.

Let’s rewind: Alvin, an affable schlub who lugs furniture for a living, is beginning to feel that the carnal parade is passing him by.

The liberating mandate of the sexual revolution is still just a rumor to him, though the idea that the rest of society is letting loose while he’s battened down in his pajamas is making him antsy.

Wally, a local public relations go-getter who likes to pretend he’s on the cutting edge, informs Alvin that “two is out” when it comes to lovemaking, and unless he wants to be “some kind of sociological throwback,” he better open himself up to ménage à trois bliss. Wally’s prurient proselytizing gives rise to the number “By Threes,” whose naughty country club revue lyrics by Stewart include such bawdy doggerel as: “Being a threesome/Your pleasures increase/More sauce for the gander/No loss for the geese.”

Complications ensue when Alvin decides that it’s Wally’s wife, Monica (Lea Thompson), who’d be the perfect addition to his Christmas Eve delight. Cleo (Vicki Lewis), Alvin’s better half, is initially aghast but, thinking one good turn deserves another, sets her sights on Wally’s handsome dapperness amid all the other holiday goodies.

This production ups the ages of this quartet from roughly seven-year-itchers to empty nesters. This change is easy enough to accept, though the spectacle of middle-age lust isn’t quite as alluring.

Nevertheless, Alexander scores the zingiest laughs during an elaborate striptease in which he mercifully calls it quits when he reaches his jungle loincloth.

Coleman is master of brassy style, but there’s no jolt here that’s on the order of “Sweet Charity’s” “Big Spender” or “If My Friends Could See Me Now.”

And Lee Martino’s delicate choreography, though executed with panache by Cassidy and droll charm by Alexander, is too careful of the performers’ lower backs to provide the necessary helium lift.

On paper, “I Love My Wife” might sound titillating, but in performance it proves staler than marathon monogamy.

charles.mcnulty@latimes.com