The first words that we hear come courtesy of an onstage Band Leader.

“It’s 1969.”

Those who didn’t know that the film of BOB & CAROL & TED & ALICE was released that year would soon infer that this new musical version takes place at least some time ago. Giving it away are all the lit cigarettes – in restaurants, airports and even a psychiatrist’s office.

Bob says that he’s 35, so he was born in 1934 – precisely when the film’s co-screenwriter Larry Tucker came into the world. His collaborator Paul Mazursky, who directed the movie as well, was four years older.

So they, along with Bob, his wife Carol and best friends Ted and Alice are all products of a pre-pill era when comparatively few dared to be sexually adventurous. Carol even reveals that Bob was the first and only man with whom she’s ever slept.

One of those times some years back resulted in conception. Thus Bob mourns that “We used to do grown-up things before we were parents.” That’s more accurate than the statement he makes only moments later: Carol and he, Bob insists, are “as hip as any couple that are parents and have a mortgage.”

Yes, many middle-agers want to be hip before they age into hip surgery. B&C know that wishing won’t make it so; at all costs, they need to feel young again,

So try The Human Potential Movement where “come to your senses” has a sensual meaning.

Bob, who makes movies for a living, says “I’m here to film.” It may well be a euphemism for “I like to watch.”

B&C are supposed to “share their feelings” for – ugh! – one continuous 24-hour span. Twenty hours in, whether it be from sleep deprivation or exhaustion, out comes hostility and truth. Bob uses the word “sorry” when talking about their marriage before adding a word that isn’t “grateful.” Carol has something on her mind, too – although it won’t turn out to be as significant as what Bob will soon do.

And what Carol will soon do, too. How civilized and urbane they are about it!

To balance their adventurousness, librettist Jonathan Marc Sherman follows the screenwriters’ lead and makes Ted and Alice skeptical and conservative. Alice refers to the ladies’ room as “the powder room” and literally orders a club sandwich because she’s at a country club.

When she sees Bob wearing a trendy man’s necklace, she metaphorically clutches her pearls. Ted is just a beat ahead of his wife: “I can’t wear beads, but they look good on you, man.”

If the show were set in the here-and-now, Alice would be yelling “TMI!” once Bob and Carol fill her in on recent exploits. What she does later say to Ted is “I don’t want to see them anymore.” She fears even the slightest of condoning from Ted; he turns out to be more enthusiastic than that. He’s been with Alice for 12 years and seems that for five years he’s not been able to reach the seven-year itch he’s been dying to scratch. As a result, the couple’s “Good night, Ted” and “Good night, Alice” are as perfunctory as what we hear when news anchorpersons say farewell to each other.

Soon Alice is admonishing Carol with an observation that is meant to bring her back to reality and brings us back to the top of the show: “We’re not kids anymore. We’re parents.” Although there’s a logical Act One curtain when Alice looks at Bob and Carol and Ted and proclaims “You’re all sick!” the 105-minute musical has no intermission.

Sherman includes many then-current expressions (“It’s where I’m at”) and reminds us of the time when “balls” was a verb. But 1969 is too early to have Carol say “Sounds like a plan.”

One then-topical reference is still valid 51 years later: Tony Bennett, then said to be performing in Vegas, is still very much singing, at least as of this writing.

Composer Duncan Sheik’s Tony-winning SPRING AWAKENING, although set in the 19th century, had characters who used microphones. They’re here in Sheik’s latest as well. While 1969 doesn’t make them anachronistic, there’s still no theatrical justification for Bob or Carol or Ted or Alice to grab a mic out of nowhere and start singing.

Why not employ lavalier-mics positioned in hair or wigs or even those cheek-mics that RENT wrought? Perhaps director Scott Elliott and/or his collaborators feel that in-your-face mics aren’t an issue anymore. The 21st century fact of musical theater life is that rock concerts were the live events on which today’s contemporary audiences were weaned. Thus these new theatergoers have taken that sensibility with them into playhouses.

Unlike SPRING AWAKENING, whose music was not at all right for the period, Sheik’s music here is era-specific down to a bit of bossa nova. He does occasionally homage (not steal: homage) Burt Bacharach, whose 1965 hit “What the World Needs Now Is Love” was recycled to conclude the 1968 film.

Enhancing his agreeable music are Sheik’s own orchestrations, with a flute and plaintively wailing saxophone well in evidence. However, the songs are more often snippets rather than full-bodied entities. Elliott keeps them flowing which, for better or worse, doesn’t ask or spur the audience to applaud each one.

There’s so comparatively little in the way of songs that B&C&T&A almost comes across as a play with music. You might even forget that this was a musical if the band weren’t sharing the stage with the actors. Again, those whose live-event experience has been mostly relegated to concerts will feel right at home.

Sheik and Amada Green collaborated on the lyrics. Which one thought of using “chlamydia” and making a new word from it? Some are deft (“lay, kid” is matched with “naked”) and some don’t quite rhyme (“Gonna give myself a waiver for a little misbehavior”). By and large, they entertain.

Carol is seen reading “I’m OK, You’re OK,” the 1967 self-help book that was still on the best-seller list when B&C&T&A hit the multiplexes. Frankly, it describes all four actors’ performances. Last Saturday afternoon, Suzanne Vega received the most applause – probably not so much for being Band Leader but for her many convincingly portrayals of many characters.

Ninety minutes in, the plot turns to – we’ll use the sexist term of the era – “wife-swapping.” “It’s something we’ve never done before,” Carol rationalizes to Ted. Fans of nudity will be disappointed, for men and women’s underwear is the most they’ll see.

Once the four are in bed, it’s almost like the final stage direction of WAITING FOR GODOT: “They do not move.”

What B&C&T&A says is that when two pairs of good friends try sex, they bring to the bed too much knowledge and history for them to freely enjoy themselves.

Fine – but the implication that they’ve learned their lesson and won’t lust for anyone anymore is specious. Sexual failure with friends can hardly be regarded as the results of an acid test. All but Alice had had good experiences with strangers on their one-night stands and the failure of the foursome cannot change that. There could well be a sequel called BOB & ROBERTA AND CAROL & CARL & TED & TESSA & ALICE & ALLEN. And they lived happily, if not ever after, well, then for that one night.

Whether or not you enjoy this one-night stand in the theater is another matter.