In Jason Robert Brown’s two-character musical The Last Five Years, boy meets girl, marries girl, and leaves girl, while—parse carefully now—girl loses boy, marries boy, and meets boy. And chronology definitely matters in this chronicle: Her songs work their way back from the end of the relationship to its dewy-eyed beginnings; his start where the romance does and proceed to its demise. They meet in the middle in a pair of rapturous duets—his proposal, her acceptance—then go their separate ways again, she getting happier, he more regretful.

It’s a nifty musical concept—half Merrily We Roll Along, half I Do! I Do!—used here to illustrate the intersection-of-(almost)-parallel-lifelines theory of romance. The paths traveled by Jamie (Mark Bush) and Cathy (Tracy Olivera) do seem, for a while, to converge, but the while is short—roughly the length of the average American marriage—and neither partner has a strong enough sense of self to permit a compromised trajectory that will allow the partnership to endure.

Partly, career paths are to blame. Jamie starts out as a budding writer, nervous when calling an agent for the first time, but he’s soon a bestselling novelist, with women hanging on his every word at book signings and a less-successful wife doing a slow burn on the sidelines. Cathy’s acting career, alas, has stalled before it could quite get established, and she’s spent too much time in bus ’n’ truck touring hell, leaving her hubby alone with his libido. It’s a recipe for marital disaster, but it doesn’t play out quite the way you expect in this backward/forward song cycle.

With Cathy’s numbers starting at the end, we hear her side first—the aggrieved wife who’s “Still Hurting,” as the title of her first song has it—while in his first song, the younger, still-unattached Jamie sounds callow and self-obsessed, very nearly a cad in the making. With this introduction, he seems solely concerned with getting ahead, she with getting along, and audience sympathies go to her almost as a reflex.

Ah, but is life ever that simple? The mature Jamie, when we finally meet him toward the end of the show, is every bit as thoughtful about their relationship as his wife. And the younger Cathy, when we later catch glimpses of her, has the same blinding stars in her eyes that Jamie did when younger. It’s their timing that’s off; she’s hardening as he’s softening.

Understandably, when the two stories mesh in the middle, there’s a tingle in the air. In song after song, we’ve heard them edge closer to a meeting of the minds, so it’s almost insanely gratifying when their voices blend for the first time and send a ballad of commitment soaring. The next song is also a duet, but this one’s contrapuntal, about conflicting impulses: He’s noticing that the girls he wanted to bed are suddenly looking at him now that he’s wearing a wedding ring; she’s missing him as she auditions for yet another touring gig. They’re still roughly in sync—enough so to be crooning the same tune—but the drift has started.

Brown’s songs aren’t earworms, burrowing into your brain with repetitive choruses, but they are pleasantly melodic, and his lyrics chart, with a mostly easy grace, the course of a relationship blossoming and fading. Jane Pesci Townsend’s smart, concert-style staging—there’s an onstage quintet of piano and strings led by music director Howard Breitbart—dispenses with all but the most essential theatrical trappings. Apart from costumer Howard Vincent Kurtz’s age-defining sweaters and hairstyles, Colin K. Bills’ hard-edged lighting effects, and a single, plot-advancing envelope, the director relies on her performers to brush in the show’s world, which ranges from New York cocktail parties to Ohio rehearsal halls populated by dwarf Tevyes and snake-charming former strippers.

Happily, Olivera and Bush are thoroughly engaging, whether belting through tears or skittering through a comic-patter song. Olivera manages to make a brave smile with a quivering upper lip mean entirely different things at the beginning and end of the evening. Bush pushes a bit in the show’s early stages, brashness not coming quite as naturally to him as sincerity, but is very funny when resisting the urge to stray and believably anguished when he stops resisting.

As accomplished as they are at conveying the evening’s odd central device, which might easily have made them appear to be giving two separate concerts simultaneously in a single venue, the performers cannot entirely overcome the limitations it imposes. Brown’s clever gimmick ends up complicating but not particularly deepening a story about characters who—in order for the tricky concept to work without being confusing—must be so simplified that, without the crossword-puzzle complexity, they might not hold our interest for 85 minutes. Sure, you pick up hints from Jamie’s songs about why Cathy’s upset, and vice versa. And yes, the sudden rush of feeling and sound during the proposal sequence acquires a certain frisson because of their general separateness. But with so much of the show rising or falling solely on the quality and delivery of individual songs, you will likely understand after a while that there’s a reason most musicals have characters singing to, at, or with—rather than past—each other.CP