The words “Glory! Sing hallelujah!” pierce the auditorium’s blackness at the outset of the Signature Theatre’s new civil-rights musical, The Gospel According to Fishman—a clarion call delivered by a African-American choir that, when the lights come up, will be revealed clustered around microphones in a ’60s-era recording studio. But for these first few moments in the dark, the sweet, clear sound of those sung words is everything—rousing, eloquent, electrified more by belief than by amplification. (Those mikes are dummies.)

If a testament were needed to the power of gospel singing, this one would easily suffice, and it’s only the beginning salvo in a musical that sends spiritual after spiritual soaring right past the rafters of Signature’s low-ceilinged warehouse. That such quintessentially Christian songs have been written by a nice Jewish boy from Brooklyn is the show’s hook. Alan Fishman, played winningly by Tally Sessions, is a lad for whom music itself seems a religion. He writes as if proselytizing, the music pouring from him in bursts of feeling.

In the story devised by Richard Oberacker and Michael Lazar, it is two African-American women—rising gospel singer Nehi Taylor (E. Faye Butler) and her pretty young ward, Jolene (Ta’Rea Campbell)—who help Alan find his voice. Nehi gives Alan’s music a springy, energized sound, and Jolene’s smile does something similar for his spirit. That’s why he signs on with them for a tour of Southern churches, playing piano and writing new material that he hopes will make Nehi a recording sensation “bigger than Mahalia” when she returns to New York, while jump-starting his career as a composer.

The problem: how to tell his family that he’s heading for Alabama with a black gospel choir at a time marked by church burnings and civil unrest. (The year is 1963.) Alan says instead that he’s summering in the Catskills, writing novelty songs for a Jewish comic his protective mother, Bunny (Florence Lacey), adores. This keeps his domestic life peaceful, but postponing the day of family reckoning puts him at the mercy of events, and when Birmingham’s Sixteenth Street Baptist Church is bombed just as Nehi is on the verge of mainstream success, the disparate threads of his life come together in a ferocious tangle.

An old-fashioned backstage musical in both style and structure, The Gospel According to Fishman works quite well in its early stages, economically establishing characters in both of Alan’s worlds and giving them plenty of opportunities to belt their hearts out. Sessions brings a sweet voice and appealing manner to the boyishly naive composer. Lacey is amusingly overbearing as Alan’s mom, and the jaunty little number in which she and her husband (Harry A. Winter) jointly kvetch about “My Son, the Writer” as Alan complains about them to the audience establishes a homey Jewish counterpoint to the gospel that powers the showbizzy scenes.

As Nehi, who’s depicted as a choir-fronting singer with attitude to spare, Butler is as ingratiating a presence as she was in 2000 in Arena’s Dinah Was. She hasn’t the sort of voice that would allow her to outshout a whole choir, but she sure knows how to sidle up to a crowd, seeming most in her element when teasing the theater audience into participating in the call-and-response that characterizes most gospel concerts. It says something about the infectious nature of the songs, and of the singing at Signature, that by the end of the first act the crowd doesn’t need much prompting.

But once the authors have finished establishing characters, they can’t seem to come up with much that’s original for them to do. Alan and Jolene hold hands and make goo-goo eyes in public, acting more like musical comedy leads than participants in an interracial romance circa 1963. (Part of the problem is that Jolene’s not much of a character as written—she’s sweet, and she has her own dreams of singing, but she’s so conventional that it’s hard to see what makes her the girl of Alan’s dreams.) Other plot points are treated in similarly perfunctory fashion. Much is made, for instance, of Alan’s withholding the news of the church bombing from Nehi until after she’s given her big performance, but there’s no real fallout from the delay. Alan later declares that he can’t write a song about the bombing, but then he manages to do so after nothing more than a short lecture on letting his emotions flow. His parents turn out to be pussycats when they finally discover what he’s been doing with his life. And though the second act has both a niftily choreographed civil-rights demonstration and a segregated lunch-counter scene, the show ultimately hinges on whether Alan will go on writing gospel tunes or switch to writing rock ‘n’ roll, or novelty numbers for Jewish comedians, or, God help him, Broadway musicals—a choice he’d have had to make even without the crash course in ’60s discrimination.

The authors have also chosen, for some reason, not to musicalize the moment in which Nehi tells Alan that he must chart his own course in life—arguably the show’s climax and certainly a moment that cries out to be sung. Instead, it’s handled as a conversation. Alan does have a number in which he ruminates on where he’s going—the title song—but it’s too flatfooted lyrically to make much of an impression.

None of which, let’s note, diminishes the galvanizing power of the show’s surprisingly varied and uniformly rousing gospel numbers. The choir’s singers are pretty damn splendid, even when they’re only marginally distinguishable from one another as characters. They keep the show pumped even though book scenes and plot-oriented songs occasionally siphon energy away, as happens increasingly in Act 2.

Credit Eric Schaeffer’s staging with illuminating character crisply and with breezing past plot problems as seamlessly as can be expected, and credit Karma Camp’s hip-thrusting choreography with powering musical moments. Both stagers make smart use of designer James Kronzer’s sliding slatted-wood panels, which stand in nicely for everything from New York recording studios to weather-beaten Southern churches.

In short, the production makes about as much of the material as can reasonably be made at this point. The authors still have some work to do if they’re to transform the historical events in which they’ve involved their characters into more than window-dressing. But their score and the winning performances of their leads mean they’re starting with a real advantage.

It’s hard to say what’s more disheartening—that Arena Stage has made such a thoroughgoing mess of On the Jump or that anyone associated with the troupe thought John Glore’s lame Cinderella fantasy worth mounting in the first place.

The company that once laid claim to being America’s leading regional theater (and that has, for three years, used an America-first-last-and-always ethos as an excuse to ignore Shakespeare, Ibsen, Stoppard, Moliere, and Chekhov) has finally found an insipid WASP romance worthy of being mentioned in the same breath as its Native American kiddie show Coyote Builds North America and its African-American sitcom Blue.

On the Jump is about a dance-hall hostess and a rich guy who meet on a bridge from which they each mean to commit suicide. She startles him and he falls. Then she seeks out his fabulously wealthy grandparents and allows them—for longer than is either conscionable or remotely plausible—to support her in a style to which she has previously been unaccustomed in the mistaken belief that she and their grandson were married just hours before his suicide. This makes her the crassest, most unsympathetic sort of gold digger—something the playwright must pretend not to notice for the duration of the play. It also makes everyone around her look like an idiot—from the grandparents, who don’t bother asking for evidence of their estranged grandson’s hours-old marriage (or even of his death) before inviting his alleged widow into their home, to the book publisher who sees a best seller in the rich guy’s depressing unmailed letters, to the rich guy himself, who (I’m theoretically spoiling the world’s most telegraphed surprise here) not only isn’t dead but is in love with the girl from afar and—get this knee-slapper—has no idea she’s the one turning his private letters into a book and defrauding his relatives.

Glore’s dispiritingly uninspired script—he sets one scene in a Chinese restaurant solely so the heroine can note that it’s fun to add “in bed” to the end of fortune-cookie fortunes—wouldn’t pass muster in a Meg Ryan movie. Nor is it helped by Wendy C. Goldberg’s staging, which encourages otherwise engaging performers to whine so much, while behaving in entirely unmotivated ways, that they end up seeming every bit as charmless as their material. CP