“The Last Five Years” is on stage, live, at Seacoast Repertory Theatre, the second in its altered summer schedule featuring three in repertory productions.

“Five Years,” penned by Jason Robert Brown, is a modern and unconventional sung-through musical. It chronicles a five-year relationship told from the perspective of its two partners. The unconventional Cathy sings the story backward in time from demise to when the couple first meets, and Jamie moves forward from the beginning through to the finish. The two timelines cross only at the moment of their marriage.

Knowing the script’s structure is important, you could easily get lost otherwise. The conceit makes for very interesting storytelling, bringing certain moments into greater focus, or giving words a more profound weight as it unfolds.

The Mad Men, Ben Hart and Brandon James, direct. The pair chose non-traditional actors, casting two African Americans in the main roles, one a woman, the other gender fluid. It’s clear what they went for was killer voices that could carry an hour-and-a-half, non-dialogue, non-stop show, featuring some heavy tunes.