Back in 1981, in a review of the original Broadway production of “Merrily We Roll Along,” critic Frank Rich observed that “to be a Stephen Sondheim fan is to have one’s heart broken at regular intervals.” While this was often due to the emotional potency of the composer/lyricist’s songs, Mr. Rich explained, it was also because “some of Mr. Sondheim’s most powerful work turns up in shows … that fail.”

“Merrily,” Sondheim’s most conspicuous flop — Mr. Rich described it in the New York Times as “a shambles,” and it closed after only 16 post-preview performances — was later tweaked by Sondheim and its librettist, George Furth, and directors have remained drawn to it; only weeks ago, Maria Friedman’s production opened on Broadway to rave reviews (mine included). I cannot, sadly, predict the same fate for Sondheim’s final work, “Here We Are,” now having its world premiere off-Broadway.

An obvious conundrum, of course, is that Sondheim is no longer around to help develop or approve revisions to the show—which is essentially an incomplete piece to begin with. When he died two years ago, at the age of 91, he was still working — as he had been, on and off, for years — on “Here We Are.” In his last interview, given days before his death, Sondheim was asked by the Times if he knew when the musical would be finished; he answered simply, “No.”

In fact, a key problem with the new show, which features a book by playwright David Ives, is the dearth of songs, if not necessarily of music. Inspired by a pair of movies by the pioneering surrealist filmmaker Luis Buñuel, “The Discreet Charm of the Bourgeoisie” and “The Exterminating Angel,” “Here We Are” follows a posse of privileged urbanites on a most unlikely journey, beginning with a fruitless search for the perfect brunch spot and culminating with them facing not only their own destruction but possibly that of humanity.

Director Joe Mantello has enlisted an assortment of beloved and rising theater stars, some also known for their screen work, to play the accidental adventurers. Bobby Cannavale turns up as Leo Brink, a caricature of a crass tycoon; he is married to the sweetly ditzy Marianne (an ideally cast Rachel Bay Jones), who goes out for the day wearing a peignoir and slippers and sings lines like, “I like things to shine — shoot me.”

Jeremy Shamos and Amber Gray play Paul and Claudia, respectively a cosmetic surgeon who just completed his thousandth nose job (“Anybody we know?” Leo asks) and a representative for “a major entertainment entity,” as she announces more than once. Stephen Pasquale appears, in a chintzy white suit, as one Raffael Santello Di Santicci, unctuous and endlessly lustful ambassador of the fictional Moranda, which is identified by another character as “some Mediterranean rat-hole.” 

Piquant instrumental music accompanies these characters, all of it expertly orchestrated by Sondheim’s longtime collaborator, Jonathan Tunick; Alexander Gemignani — son of Paul Gemignani, another Sondheim stalwart, and a veteran of the composer’s work as both a performer and a conductor — leads the orchestra and furnished additional arrangements. Yet the actual songs, if you can call them that, feel more like rough drafts than finished works by one of the greatest composers and lyricists to ever work in any genre.

In the first act, a waiter played by the redoubtable Denis O’Hare, who’s superb in a number of roles — mostly working stiffs, though one emerges as rather spectacularly, and darkly, ambitious — leads a parody of contemporary culinary quirks, with lyrics that suggest an homage to Sondheim’s flair for wordplay by one of his many acolytes. “We haven’t got a lotta latte now,” the waiter sings; he then laments, “Not only are we out of Earl Grey/ We’re out of Earl Green/We’re out of Earl Red and Blue/And everything in between.”

A pair of mismatched young lovers — an earnest soldier portrayed by Jin Ha and a sulking activist played by budding star Micaela Diamond, fresh from her luminous performance in last season’s Broadway revival of “Parade” — get a sort of quasi-duet that barely hints at the visceral power that, for all the attention paid to Sondheim’s preternatural cleverness, was his most enduring gift. Early in Act Two, Marianne offers a few brighter flashes in a wistful manifesto that proves to be the last thing approaching a sung-through musical number in the show. 

There are moments that follow, mind you, that practically scream out for the kind of transcendent release that songs provide in musical theater, that Sondheim offered countless times through his last great work, 1994’s “Passion.” At one point, a bishop who winds up joining the other characters — played to deadpan perfection by a predictably stellar David Hyde Pierce — agrees to explain “being” to Marianne; tender music twinkles promisingly under his monologue, so it’s almost painful when a song doesn’t emerge. 

All of which raises the question: Was it necessary, or even fair, to bring “Here We Are” to the stage? It was, I’m sure, a quandary that the Stephen Sondheim Trust, listed prominently among the producers, labored over: whether to present to the public a clearly unfinished score by a theater artist of unsurpassed magnitude, or to keep those efforts hidden, lest they blemish his legacy.

Judging by the nearly unanimous standing ovation that “Here We Are” received at the preview I attended — a tribute to Sondheim’s larger body of work, I suspect, and the generally excellent performances culled by Mr. Mantello — it wasn’t the wrong decision. To quote a lyric from one of Sondheim’s many celebrated earlier shows, the experience left me “sorry-grateful, regretful-happy” — and I wouldn’t have missed it.