In the 1976 movie The Man Who Fell to Earth, the pop chameleon David Bowie plays an alien who does his best to pass as human while trying to figure out how to share Earth’s abundant water supply with his drought-choked home planet. Girlstar, a slick and amusing but deeply confused new musical at Signature Theatre, is derived from far less obscure sources: the Disney princess factory and singing-contest TV shows. But in its perception of how pop music gets made, this glossy, pink-frosted fable could just as well be an extraterrestrial’s attempt to reverse engineer it after mainlining every single episode of American Idol and The Voice during a sleepless, years-long journey from another galaxy. What it lacks in music-industry veritas, or insight into how talent is nurtured or songs get written, it makes up for—sort of—in bright melodies and attractive actors. That is both far from nothing and not nearly enough.

In plotting his story of the rise and fall of Tina, who is winsome and a nice person but exhibits no skills that would seem to make her a candidate for divadom, book writer and lyricist Anton Dudley betrays a puzzling belief: Smooth moves, glass-shattering pipes, and some offstage string-pulling are all it takes to become a pop idol. (Try telling that to Beyoncé, who stands for nothing if not Sasha-fierce determination and practice, practice, practice.) It’s curious that a professional songwriter would so completely discount the role of, well, songwriting. It’s as if every cranky parent’s claim that whatever singer their kid likes is just the vapid product of studio engineers and makeup artists (and in this case, supernatural voodoo) were literally accurate. That sounds like a rich proposition for a musical, but Dudley’s script doesn’t exploit it well because he hasn’t decided whether his heroine is a genuine talent or a deluded fraud.

The casting of the marvelous Desi Oakley as Tina only clouds the issue. She looks and moves like the flesh-and-blood incarnation of a Disney feature animation leading lady, and she can sing. (It’s a Signature Theatre show. Everyone here can sing. But Oakley has obvious star power.) Whether her character is meant to share these gifts remains maddeningly out-of-focus. Case in point: In “Tonight,” the song that introduces Tina, she stands on a picnic table, pretending to preen before adoring thousands. In her hand is a guitar—her dead mom’s guitar, she tells us, which she’s just found. She cradles it like a baby. She waves it around like a baton. What she never does is even attempt to play it. Not every musician is a guitarist, but if she isn’t, why choose that object to link Tina to her mother? If she has a musical molecule in her, wouldn’t she at least try to strum a few chords?

Perhaps because the heroine is so vague, the show opens with its villain. Signature stalwart Donna Migliaccio plays Danielle Espere—essentially Cruella de Vil reimagined as a kingmaking record producer. A video prologue informs us that as a child Espere murdered her sister and harvested her musical talent in the form of a glowing green liquid (you might call this the Midichlorian Theory of talent transfer). Strangely, Danielle never evinces any hunger to make herself an object of adulation. Rather, she wants to engineer the ultimate pop star by fracking out the individual talents of the performers in her stable and then infusing all that green goo into one ripe vessel.

Espere finds a suitable dupe in Tina, her long-lost niece. Raised by her Uncle Derek (Bobby Smith), who forbade her to listen to music (Q: “Why would you want to live in a world without music?” A: “Because it hurts too much!”), Tina is easily seduced by the cushy life Espere offers. Her wicked aunt wastes no time raiding her existing client list for spare parts: She takes Piper’s pipes and Neela’s dancing ability, and injects them into Tina, just in time for “the live E concert,” whatever that’s supposed to be.

You know what works? The Esperes, a trio of singers and dancers played by Kellee Knighten Hough, Nora Palka, and Bayla Whitten, who follow Espere around. They all sound great, even if their execution of Lorin Latarro’s choreography isn’t quite in lockstep synchronization. They wear Frank Labovitz’s costumes, which are informed by glam and punk without embracing any particular era, with elan.

Sam Edgerly’s sweet-natured Jeff—a concierge at the luxury hotel where Espere installs Tina in her penthouse—is the only character who ever gets down to the lonely, frustrating task of actually trying to write a song. Whether or not Tina will ever return his affections on something other than a platonic level is agreeably murky—it’s the one part of the show wherein the air of indecision actually works.

4200 Campbell Ave., Arlington. $40–$96. (703) 820-9771. sigtheatre.org.