Since If/Then premiered on Broadway in March 2014, several theater writers have commented on how the range and power of lead diva Idina Menzel transforms Tom Kitt and Brian Yorkey’s so-so musical into a show well worth seeing.

Suffering through Kitt’s bland, homogeneous melodies at a touring performance at the Pantages this past weekend, only the so-so assessment of the material seemed on the mark. An indifferent performance by Menzel helped intensify every yawning detail of this lusterless spectacle, whose shortcomings were underscored by faulty sound tech that rendered the first few numbers and their intermittent dialogue almost incomprehensible.

The highfalutin gimmick in Yorkey’s book is the bifurcated plot. Elizabeth (Menzel) a college professor of urban planning, returns to New York from Phoenix following the collapse of a 12-year marriage. Whither her new life? Will it be a fresh start to her career or a budding new romance?

The answer is both, as the narrative splits and the character assumes a double identity (rather like Gwyneth Paltrow in Sliding Doors). As Beth she’s hired as a city planner, where over the years she gains fame and respect and has an affair with her dishy married boss (Daren A. Herbert). As Liz she meets an equally fetching soldier (James Snyder) who adores her. She marries him and starts a family.

Ideally, one is supposed to be able to distinguish between these narratives by whether the performer is wearing glasses and by changes in Kenneth Posner’s lighting design. The reality is, it’s not always easy to tell or, more to the point, to care.

Directed by Michael Greif, If/Then is basically a sort of Wonder Bread story about a middle-class professional inhabiting a mythically sparkling and crime-free Manhattan. You can get away with that fantasy if you’ve got some irony or farce or plain old humor in your narrative but not when you’re expecting your audiences to swallow this hokey stuff straight.

Of course, the subplots do embrace same-sex couples, and there’s broad ethnic diversity in the casting. Kudos for that, at least.

Both Larry Keigwin’s choreography and the dancers who execute it are uninspired. There’s solid work, though, from both Herbert and Snyder, who’ve invested some of themselves in their roles. Anthony Rapp as Elizabeth’s bisexual ex-boyfriend also has his moments, and when he sings “You Don’t Need to Love Me,” it’s actually affecting, unlike most of the music, which — and this may have been the tech levels again — just didn’t sound that good.

Menzel, whose singing displayed volume but little passion, has her best number near the end. It’s called “Always Starting Over” and she sings it against the backdrop of a starry sky. One couldn’t help but wonder if, seemingly bored with this role, she wasn’t ready to start over in an entirely different show.

Pantages Theatre, 6233 Hollywood Blvd., Hollywood; through Jan. 3; (800) 982-2787, hollywoodpantages.com.

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