Marriage can be a lonesome business.

That's the poignant truth at the heart of "The Last Five Years," Jason Robert Brown's ingenious two-actor musical, and it's a truth well illustrated in the spare, classy production of the work running at MetroStage under Jane Pesci-Townsend's direction. Watch the entrances of Catherine and Jamie, the incompatible lovers/spouses portrayed by Tracy Lynn Olivera and Mark Bush: They stroll onto the stark gray stage from opposite directions, pause in the center, just inches from each other, and move on, their glances never crossing. Forget "Till death do us part" -- these two have obviously spent wedlock on separate planets.

"The Last Five Years" imparts its rueful insight through a clever gimmick: The story of Catherine and Jamie's courtship, marriage and separation unfolds in two directions at once. Jamie's songs -- there is virtually no spoken dialogue -- bowl along chronologically, from elated infatuation ("Shiksa Goddess") to resigned farewell ("I Could Never Rescue You"). Catherine's numbers sneak backward through time, from elegy ("Still Hurting") through early love ("Goodbye Until Tomorrow"). The two trajectories cross briefly in one romantic scene, set on a boat in Central Park. Before and after that, alternating solos relate Jamie's meteoric success as a novelist, juxtaposed with Catherine's washout acting career as she squirms through bad auditions and Ohio summer stock.

The contrasting energies of these two lives smolder, clear and sad, in Olivera and Bush's creditable performances, although both actors get off to a rickety start. Olivera's lovely, vibrato-etched voice soars achingly through the early numbers, but that can't quite compensate for her inability to make her character's dejection interesting. For the first third of the show, Catherine is frozen in misery, her intonations unvarying, her movements stilted. But as the role's reverse-chronology gains momentum, the performance thaws. Wicked smiles creep over the actress's face, her posture relaxes, and we suddenly realize that Catherine can be witty and charming, as she is in the delectable letter-writing song evoking her Ohio exile ("I could chew on tinfoil for a spell! / I could get a root canal in Hell, / But it wouldn't be as swell / as this summer is gonna be!").

Bush is a more seductive comic actor, and he gives the story considerable edginess with his depiction of the cocky Jamie -- breaking out into a strutting dance, gesturing triumphantly with his cell phone, placing his baseball cap backward, sassily (the low-key costumes are by Howard Vincent Kurtz). But his singing skills are weaker, and portions of some numbers, especially his first, seem a shade too low for his range. Still, he's a clear conduit for Brown's sly and often hilarious lyrics ("I left Columbia and I don't regret it / I wrote a book / and Sonny Mehta read it!").

The backbone of the production, though, is the team of terrific musicians who sit on a raised tier at the back of the stage, underneath the three white-framed windows that are the sole set elements. Led by musical director Howard Breitbart at the piano, these instrumentalists have a beautifully pure and expressive sound that highlights the classical inflections in Brown's score. And in a number like the wrenching finale, the musicians are able to delineate and balance two polarized moods: the euphoric piano-dominated strains underscoring Catherine's new amorousness, and the wistful melody of the strings acknowledging, with Jamie, that love has died.

The Last Five Years, written and composed by Jason Robert Brown. Direction and scenery design by Jane Pesci-Townsend; lighting, Colin K. Bills; sound, Matt Rowe. Approximately 90 minutes. At MetroStage, 1201 N. Royal St., Alexandria. Call 1-800-494-8497 or visit www.metrostage.org.

Mark Bush and Tracy Lynn Olivera as a married couple on the skids, with Bush, right, adding considerable edginess and sass to his role, in "The Last Five Years."