Before the curtain rises on the new musical “Gettin’ the Band Back Together” at the Belasco Theatre, Ken Davenport, the show’s lead producer, who also co-wrote the book, takes the stage to warm up the audience with a little friendly patter. (Davenport alternates in this hosting role with other members of the show’s team.) He points out with pride that the show is “one of those rare things on Broadway these days: a totally original musical.”

Hmm. Methinks the producer doth protest too much. For while it’s true that the show, unlike a hefty proportion of “new” musicals these days, is neither adapted from a movie nor constructed to showcase an already established hit parade of songs (and yes, kudos on that front), to call it truly original would be overstating the case. The arc of both its primary storyline (see the title) and its many subplots are so grindingly predictable that the whole show might have been assembled by a pop culture algorithm tuned to maximize sentimentality. (There are also notable similarities to “School of Rock,” a movie-turned-musical.) Although the show has an appealing modesty and goofy humor, fresh it certainly is not: In fact the show itself winningly pokes fun at the inevitable climax, when the good-guy band and the bad-guy band both (surprise!) reach the finals of an annual competition to be champs of “Western Eastern Central Middlesex County.”

Mitchell Jarvis plays the protagonist, Mitch Papadopolous, who in the opening scene turns 40 and is promptly fired from his banking job in New York. Licking his wounds, he heads home to New Jersey and moves back in with his mother, Sharon (Marilu Henner). His old pals, with whom he once formed a band, are still in town, variously mired in the doldrums of young middle age.

The schlubby Bart (Jay Klaitz) teaches math, although he’s barely mastered the basics. The doctor Robbie (Manu Narayan) works in his father’s dermatology practice. Sully (Paul Whitty) is a cop sullenly studying to earn his detective’s badge. The primary plot is set in motion when we learn that both Sharon and Bart’s homes are being foreclosed on by Tygen (Brandon Williams), Mitch’s arch-foe, an amateur rocker who now controls much of the real estate in town, who challenges Mitch and his band to a rematch of their youthful rock-off. Tygen agrees to forgive the mortgage debts should Mitch’s band win, as they did decades ago.

Oddly — albeit conveniently for the ample supply of subplots — neither Mitch nor his ex-bandmates have a love interest at first. But such is the show’s formulaic nature that romances blossom every time a female character appears onstage. The couples might as well wear matching T-shirts, so obvious is it who will pair off with whom.

Bart sheepishly admits he always thought Mitch’s mom Sharon was a “MILF,” and sure enough they soon hop into bed. (Not as creepy as it might seem, since the preternaturally lithe Henner looks roughly the same age as her son’s pals.) When a female fellow cop exchanges friendly banter with Sully (learning he was a drummer, she gushes, “I love the drums”), we can practically hear the wedding bells. And of course when it is revealed that Mitch’s old high school flame Dani (Kelli Barrett) is now dating Tygen, it’s clear that the battle of the bands will be matched by a brawl for Dani’s heart.

If the book, by Davenport and a collective called The Grundleshotz, who developed the show “through a series of improvised rehearsals,” doesn’t strike many unforeseeable notes, nor does the churning pop-rock score, by Mark Allen. Nodding to the Jersey setting, the rock anthems echo the arena sounds of Bon Jovi, as well as the eardrum-shattering volume, while the softer songs are sonorous but mostly bland ballads in which the characters lament their half-wasted lives and yearn for “Second Chances,” as the title of one of the songs bluntly puts it. (The gag about Bruce Springsteen’s concurrent Broadway stint rather awkwardly points out that Allen’s serviceable rock doesn’t favorably compare with that of other famed Jersey natives boys.)

“Gettin’ the Band Back Together,” which is directed at a brisk clip by John Rando, features charming sets, by Derek McLane, that often suggest Saturday morning cartoons of yore, or maybe a Charlie Brown TV special, neatly winking at Mitch’s regression to pseudo-youth. But those cartoon qualities also underscore a similar two-dimensional quality in the characters and the “Scooby-Doo” obviousness of the plot.

That said, the musical is not without its splashes of ribald or bleakly funny humor. (“I Told You I Was Sick” reads one of the tombstones at the cemetery where the ex-bandmates go to visit the grave of the one member who died.) And the performers give appealingly smooth grease to the mechanical proceedings.

As the math teacher Bart, Klaitz is particularly vivid in his goofy exuberance. Whitty brings a sad-sack sweetness to his role as the cop Sully. And as the preeningly arrogant Tygen, whose permatanned and tattooed body and bedazzled jeans announce his fulsome, “Jersey Shore” vulgarity, Williams makes for a snarling doofus of a villain, dripping testosterone and hair gel, and forever quoting his father’s aphorisms without managing to get to the point of any of them. (A funny running gag finds his sidekick and bandmate Ritchie, pungently played by Garth Kravits, interrupting Tygen with samples of his father’s actual but less edifying bits of advice like, “If you’re facing twenty to life, it’s OK to squeal.”)

Also providing appealing diversions are Sawyer Nunes as Ricky Bling, a would-be Eminem who is recruited to replace the band’s dead guitarist, and who turns out to be a nice Jewish boy who can rap his way through “Hava Nagila,” in one of the show’s liveliest and freshest musical numbers; and Noa Soloario as Dani’s grumpy, foot-stomping, goth-punk teenage daughter. (Lest any of the show’s characters be left out, these two naturally find romance too.) The other women’s roles, unfortunately, don’t allow for much coloring outside the broadly drawn lines.

As Mitch, Jarvis gives a likable if hardly galvanizing performance in the central role, singing with a piercing rock tenor that slices easily through the guitar-driven arrangements, and acting with a becoming soft touch. It’s not Jarvis’s fault that Mitch, a good-hearted guy with a bit of a hole in his heart, come across as just an average Joe in an average musical.

“Gettin’ the Band Back Together” opened at the Belasco Theatre on Mon., Aug. 13, 2018. 

Creative: Book by Ken Davenport and The Grundleshotz; Music by Mark Allen; Lyrics by Mark Allen; Directed by John Rando; Choreographed by Chris Bailey; Scenic Design by Derek McLane; Costume Design by Emily Rebholz; Lighting Design by Ken Billington; Sound Design by John Shivers.

Producers: Produced by Ken Davenport, Hunter Arnold, Roy Putrino, Sandi Moran, Carl Daikeler, Broadway Strategic Return Fund, Rob Kolson,H. Richard Hopper, Richard Roth, Marie Barton Stevenson, Diego Kolankowsky, Marguerite Hoffman, Brian Cromwell Smith, Darrell Hankey/Trevor Coats, Witzend Productions/David Bryant, Jim Wagstaffe/Laura Z. Barket/Rich Battista, Judith Manocherian/Mach 1 Partners/John McGrain and Steve Reynolds/Ladybug Productions/Barry Tatelman.

Cast: Mitchell Jarvis, Kelli Barrett, Marilu Henner, Jay Klaitz, Becca Kötte, Garth Kravits, Tamika Lawrence, Manu Narayan, Sawyer Nunes, Noa Solorio, Paul Whitty, Brandon Williams, Ryan Duncan, Nehal Joshi, J. Elaine Marcos, Rob Marnell, Jasmin Richardson, Tad Wilson.