It has finally happened. No longer must we stare into our laps, abashed and mute, as a previous generation of playgoers speaks of “Carrie” and “Prince of Central Park.” No longer will their fathers and mothers, in turn, silence the room with stories of those mythic flops “Portofino” and “Kelly,” the years falling away as the still-vivid memories flood from their stricken mouths. Every generation seeks its jaw-dropper, its howcould-that-have-reached-Broadway-andhow-could-I-have-missed-it disaster. And despite the best efforts of “Dance of the Vampires,” “Thou Shalt Not,” “Good Vibrations,” and so many other terrible musicals of recent years, the rubberneckers of Broadway have found their fears and hopes repeatedly dashed. Until now.

Any attempt at summarizing “In My Life,” an appallingly hubristic lite-FM tale of love in the time of Tourette’s syndrome, will inevitably fall short, but here goes. Blond boy and blond girl meet cute and move in together. Except the boy has Tourette’s. And the girl’s pal’s boyfriend killed the boy’s mother and sister in a car crash. And the boy has a brain tumor. And his dead mother sings an aria in Italian. And God takes a vacation, deputizing a fey dead accountant to produce His “reality opera” (which I take to mean life on earth). And the fey accountant flies on and off the stage, dances with a skeleton, and says things like, “Oh no, she didn’t!” And God sings actual 1970s commercial jingles for Volkswagen and Dr. Pepper. And the dead sister walks around in a tutu in heaven and asks the guy who killed her if he wants to ride her scooter. There is no intermission.

Actually, the one thing in the plot that does make sense is the part about the jingles. See, Joseph Brooks wrote those tunes and many others, not to mention the easy-listening megalith “You Light Up My Life,” back in the 1970s. Joseph Brooks also wrote the music, lyrics, and book to “In My Life,” in addition to producing and directing it. In other words, Mr. Brooks decided that God, were He so inclined to convey His wishes through song, would turn His robust tenor to Joseph Brooks jingles. Now who’s omnipotent?

The rest of the score actually pales in comparison to “(You Gotta) Listen to Your Mouth.” One midtempo song after another chugs through, each less distinguished than the next. (For the record, “I Am My Mother’s Son” has a crisp, perfectly nice folk-pop melody.) The unflaggingly perky tunes fade from memory even before their third and fourth reprises, but the lyrics will not be forgotten anytime soon.

One song actually begins with the line “In this time called life.” Another includes this couplet: “I’ll climb out from the lost and found / And try to turn my life around.” And the book! Not since “Deuce Bigalow: Male Gigolo” has Tourette’s syndrome served as such a fertile source of humor, and the lead characters express happiness by shouting “Lemon!” (The fearless Mr. Brooks has tempted fate and critics everywhere by putting enormous lemons both on the stage and in the show’s poster.)

“In My Life” has reportedly gone through extensive changes during previews, cutting down on the wrong sort of audience laughter in some cases and streamlining the “plot” in others. But a few questions remain: Was the real God on vacation when lines like “I need this relationship like I need sand up my butt” were written? When will sassy gay ectomorphs finally begin to fade as fallbacks for cheap laughs? And what must costume designer Catherine Zuber and lighting designer Christopher Akerlind, both Tony winners for their exquisite “Light in the Piazza” work, have thought as they came to work each day with a seemingly unlimited budget and no pressure to harness their skills to anything resembling a compelling or even coherent story? Allen Moyer’s sets are similarly lavish and ludicrous.

The cast’s vocal talents are terrific across the board, and Roberta Gumbel (as the dead mom) is even better. Beyond that, though, it is nearly impossible to judge the talents of those on stage. With the exception of Ms. Gumbel and a droll Michael J. Farina as a schlumpy God, everyone comes off terribly. How could they not? All they have to work with is a grisly blend of whimsy, in-jokes, turgid melodrama, and maudlin emotions. They’ll get their rewards in months and years to come, whenever they attempt to pay for a drink within earshot of a musical-theater buff.

“In My Life” also represents a new low point in the tail-chasing phenomenon of self-referential insider Broadway gags, resorting to “Peter Pan” and even “Dirty Rotten Scoundrels” jokes in one recent performance. A less overt but more telling allusion can be found in one of Mr. Moyer’s sets, a cluttered New York apartment that features a familiar black-and-white photo of the John Lennon “Imagine” memorial in Central Park.

If you were to make the somewhat drastic assumption that things happen in “In My Life” for any reason at all, you might suspect Mr. Brooks was trying to remind his unfortunate, blessed audience members of the last disastrous musical to reach Broadway, “Lennon,” perhaps encouraging us to count our blessings. Who would have guessed that only 10 weeks later, we would look back on that hard-sell inanity, a genuine low point of recent musical theater, as nothing more than a curtain-raiser? “Lennon” was merely awful. “Moose Murders,” meet your match.

(239 W. 45th Street, between Broadway and Eighth Avenue, 212-239-6200).