It’s an old, familiar tale, delivered at half-throttle

Barry Mann and Cynthia Weil’s solid gold catalog of heart-pumping love songs might seem to qualify them to score a musical based on the baldly sentimental 1985 movie “Mask,” about a doomed teenage boy with a rare disfiguring bone disease trying to be normal. But in this world premiere at the Pasadena Playhouse of screenwriter Anna Hamilton Phelan’s adaptation of her own, earlier work, the music and story too often elude each other, keeping the show from finding a rhythm that can carry it convincingly through 2 hours, 45 minutes.

When a play or musical derives from a popular movie, even one more than 20 years old, it is hard -- if not impossible -- to put the film out of your mind, certainly when staged within commuting distance of Hollywood.

The film, directed by Peter Bogdanovich, was notable for its performances by Eric Stoltz, Cher and Laura Dern, playing, respectively, the disfigured but plucky Rocky Dennis, his pill-popping biker mom and the beautiful blind girl who falls in love with him. In “Mask,” the musical, directed by Richard Maltby Jr., Allen E. Read, a young actor with a wonderful, emotive tenor, makes Rocky every bit as vivid and touching as Stoltz did. In the other two roles, however, the actresses tend to remind us of how good Cher and Dern were on-screen.

The main set, by Robert Brill, provides a painterly evocation of the Southern California suburbs, with a hazy sky dominated by power lines, dark palms and the crests of the San Gabriels. It is humble Azusa, to be precise, where Rusty and Rocky, a combative mother and son surviving on her waitress tips, struggle with the double burdens of Rocky’s disease and her drug addiction but are buttressed by the benevolence of a local biker club that serves as their extended family.

A biker clan revealed as an unexpected cradle of homespun values is a hard sell, but it’s the sort of transaction made possible through the wiles of Hollywood and musical theater.

Meanwhile, the image of the roaring chopper aimed at the endless freedom of the open road fuels both Rocky’s dreams of escape and -- in the creators’ design -- our own. “I Ride With Rocky” buttons are available in the lobby.

Busy scenes and songs depicting Rocky’s challenging life at public school serve to highlight his courage, grace and wit in the face of unthinking cruelties and the recurring headaches that portend his fate. Doctors inform him he will not live to be 17, but he fortifies himself with good thoughts and the vision of a cross-country cycle-driven odyssey.

For the stage version, Mann and Weil have come up with some sturdy rumble-ready anthems that feed the well-worn born-to-be-wild motorcycle rebel mythology. Unfortunately, the cast does not always seem capable of delivering them at full throttle.

Michael Lanning, who plays Dozer, the beefy father figure of the Tribe and its lead vocalist, shows evidence of having a big voice at times; at others, he seems merely to be growling somewhere beside the melody -- as when he sings “Close to Heaven,” describing to Rocky the transcendent experience of cruising the Black Hills of South Dakota on the way to an annual bikers’ convention.

Michelle Duffy, who was so good in the leading role of Pistache in the revival of “Can-Can” at the Playhouse last year and is technically quite the singer, is less effective with the admittedly tricky assignment of Rusty, Rocky’s low-rent, high-maintenance mom, who must be both hateful and tender and must deliver several unwieldy numbers.

These include the Act 1 closer, “Look at Me,” a frantic duet with Rocky staged amid swiveling fun-house mirrors, and “I Can’t,” her cathartic Act 2 explanation to the Tribe (during an intervention) that her drug abuse is all about enduring the tragedy of her misshapen son. And for some reason, she bestows on Rusty an intrusive Brooklyn accent.

Although the show is too long and lacks cohesion, there are moments where the pedigree of its composers shines through. Mann and Weil, whose Songwriters Hall of Fame credits include “You’ve Lost That Lovin’ Feelin,” “Soul and Inspiration,” “Just Once” and “We Gotta Get Out of This Place,” have fashioned a sweet duet for Rocky and Diana (Sarah Glendening), “It’s a Beautiful World,” to dramatize the scene at the camp for the blind where he teaches her the meaning of colors. “Planet Vulkturn,” Rocky’s stoically defiant response to being rejected by Diana’s parents (“I won’t pity you if you won’t pity me”) is another song you might hear on the radio if, so to speak, there were still songs on the radio.

Others are more problematic, either in concept or execution, including the tedious “Do It for Love” attached to Rocky’s star turn in history class explaining the importance of sex to the outcome of the Trojan War and “A Woman So Beautiful,” the tribute to Rusty sung by her on-again, off-again handsome motorcycle man Gar (Greg Evigan).

“Based on a true story,” “Mask,” the musical, is in ways more mawkish than the film. During the early number “Every Birth,” describing every mother’s hope for her newborn, slide projections reveal photographs of Rocky as a normal-looking adorable baby, followed by clinical pictures of his later, slowly emerging freakishness. Ouch. Try adding music to that.

And yet even as the show parades such unbearable sadness, it also devolves into the crowd-pleasing shtick of Rusty pulling a drug stash out of a box of matzo and managing to have Rusty and Gar married by a hippie rabbi.

We know how the story is going to end, but this time, through the magic of the theater, Rocky is able to make a posthumous reentrance on a gleaming chrome-and-white chopper that he can ride into heaven. Perched above the stage, he triumphs over the mortality that has cursed him and goes out in a thunder of power chords with the previously deceased Dozer at his side.

Read, wearing a flesh-colored mask created by the same makeup man (Michael Westmore) who worked on the film, does reach the sky at times with his singing. But his achievement alone can’t rescue this overwrought idea from itself.

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‘Mask’

Where: Pasadena Playhouse, 39 El Molino Ave., Pasadena

When: 8 p.m. Tuesdays through Fridays, 4 and 8 p.m. Saturdays, 2 and 7 p.m. Sundays. Exceptions: No 8 p.m. performance Wednesday; 2 p.m. only on April 2

Ends: April 13

Price: $38 to $76

Contact: (626) 356-PLAY, www.Pasadenaplayhouse.org

Running time: 2 hours, 45 minutes