• Courtesy Of Lindsay Raymondjack
• From left: Connor Kendall, Coleman Cummings and Kianna Jensen Bromley in tick, tick... BOOM!

A story often hits harder when viewers know it's true, and tick, tick... BOOM! is — at least as far as make-believe musical comedy can be. The composer Jonathan Larson wrote an autobiographical monologue in 1991, when his career seemed stalled. It wouldn't be long before Larson broke through with the prize-winning Rent, a Broadway success he didn't live to see. Converted to a three-person musical after his death, BOOM! is Larson's story of early disappointment and unshakable hope. The Vermont Stage production bounces with youthful conviction.

The show begins with a ticking clock as Jon tells the audience he's dreading his 30th birthday: If he hasn't succeeded in getting a musical produced by 30, he fears he never will. And he wonders if he should keep trying as he watches his best friend, Michael, settle into affluence as a marketing executive and listens to his girlfriend, Susan, question whether she should leave New York.

Jon lives in a fifth-floor SoHo walk-up, scratching out songs and working as a waiter. He confesses that his idol is Stephen Sondheim, a name he whispers out of beatific respect. And then the songs take over, telling Jon's story with a rich homage to Sondheim ("Sunday"), a funny patter song duet that's also a duel ("Therapy"), a soaring number ("Come to Your Senses") that kicks off the show's four-song climax and a dozen more.

The comedy is clever, but audiences may laugh most as the two supporting characters spring into multiple roles. The actors playing Michael (Connor Kendall) and Susan (Kianna Jensen Bromley) make small, swift costume changes to fill out Jon's world. Coleman Cummings, as Jon, whirls with a striver's energy. Even the props are semi-magical, hidden behind multiple locker doors for the actors to retrieve.

Jon doesn't face big obstacles, just fears. And those fears are only interesting because of events that stand outside the show itself. One of his fears now seems tragic (he's wary of his 30th birthday but won't live longer than his 35th), and another seems silly (he frets he hasn't achieved enough but is a few years away from revolutionizing musical theater). Within the show, it's all too clear his career doubts won't stand in his way — they barely register.

Cummings and director Cristina Alicea bathe Jonathan in the bright glow of creative certainty. The story screams that nobody's stopping this dreamer, and Cummings portrays him always revving up for a bust-out dance move, balancing on the toes of his sneakers. No money and an indifferent agent count as problems, but Jon faces no blocks to his artistic drive and always has his friends' support. What he feels he doesn't have is time.

The musical's structure is missing any real rock bottom — and, for that matter, doesn't rise much higher than its starting point, either. The pleasure for viewers is not in the little impulse to whisper to the hero (and also to ourselves) not to give up. It's in watching buoyant youth charge forward, aware that life is short.

Larson only wrote three full musicals. His first, the unproduced Superbia, never got past the workshop stage, which gives the character in BOOM! his feeling of failure. His final musical, a fuller look at the seize-the-day theme he explores in BOOM!, is the remarkable Rent, which swept the theater awards in 1996, winning the Pulitzer Prize for Drama and the Tony, Drama Desk and New York Drama Critics' Circle awards for best musical.

Larson died suddenly the day before Rent's first performance in 1996. In 2001, the playwright David Auburn reworked Larson's monologue into a musical with characters and scenes.

Alicea and choreographer Carissa Bellando fill the smallish stage with big gestures. Alicea responds to the show's stripped-down cast size and the Black Box Theater's limited playing space by emphasizing motion. The characters swoop and dive in the musical numbers but bustle just as much in straight scenes. Jon personifies a man in a hurry, and Alicea helps us see that best when she occasionally boxes him in immobility or leaves him swashbuckling through a song while the supporting actors calmly observe in stillness.

Bellando gives Jonathan and Michael some good-times dance moves that wouldn't be out of place on a peppy soda commercial. As a dancer, Susan earns more engaging choreography, though Bellando overdoes the drama in one number, losing the show's gritty tone. Overall, the movement expresses youth itself.

Cummings radiates energy for the full, intermission-free 90 minutes. He's a solid singer with a bright collection of entreating looks. All that's missing is a layer deeper than earnest — but, boy, can he yearn.

Bromley shows Susan wavering between commitment to Jon and a need to grow up, at least a little. For each of her smaller characters, Bromley supplies sharp comic details in voice or manner. And her strong, emotional vocals, especially on the knockout "Come to Your Senses," brighten the show.

While Jon wrestles with shallow doubts, Kendall portrays Michael quietly facing deeper ones even as his career ascends. He's left a creative childhood for the fake creativity of marketing, and now his playful side is masking fear. Kendall gives him a quirky tenderness.

Larson's melodic songs are suited to rock-pop orchestration, and many tunes have the hammering piano howl of Billy Joel. Others rest on jazz-inflected harmonics. Each performer has a standout solo, but most songs depend on three voices in haunting harmony, which the miked cast couldn't always deliver on Thursday but will probably find during the run. A live four-person band, headed by musical director Nate Venet, sits in silhouetted view above the stage.

A driven young guy lamenting his professional anxieties may seem indulgent, but what's driving him is the pressure on us all: Time is fleeting. We might want to live it like Jon, singing a song as loud and long as we can.