Berkeley Rep kicked off its new season this week with a new musical piece by a pair of talented performers and musicians that delves into a mostly untold piece of pre-Civil War history.

Billed as a "live-looping musical," Mexodus is a wholly unique piece of theater built around music that's being layered and looped live on stage, using loop stations — mixing devices that record and play back several-second loops of sound. If you've never seen musicians work with loop stations before, it can be a beguiling and moving experience, the quick, sometimes improvised creation of on-the-fly, beautifully layered tunes is a winning party trick.

Sometimes, what's being done in Mexodus isn't even music, but just simple, analog sound design with a digital aid — like when one character crumples some paper onto a loop to mimic the sound of a crackling fire, and then sits in the glow of this "fire" in a perfect moment of old-school clowning.

Co-creators and performers Nygel D. Robinson and Brian Quijada spin a fictional tale about Henry, an escaped slave blamed for a murder in Texas — which was actually a self-defense killing — who flees to Mexico, on the little-known "Underground Railroad that went South." He makes this escape with the help of a rancher across the boarder named Carlos, who has his own bitterness toward the US, and the two form a bond.

Mexico had outlawed slavery in 1829, well before the US ultimately would, and historians believe that around 4,000 to 10,000 escaped slaves fled to Mexico and established communities there. The most notable of these was the Mascogos, a group of Black Seminoles and formerly enslaved African Americans who settled in the state of Coahuila, and formed a town that became known as Nacimiento de los Negros — literally Birth of the Blacks. (While the town has only a small number of Mascogo descendents now, it still celebrates its own version of Juneteenth, dubbed "Dia de Los Negros.")

Mexodus only barely delves into this history, opting instead to focus on the story of one fictional man and his fictional host on this Underground Railroad. The piece is at its strongest when Robinson and Quijada let loose in one of their bits of rap storytelling, or when they harmonize beautifully in relaying their characters' respective trauma.

At 100 minutes with no intermission, the piece still feels like a bit of a work in progress that could be more taut — some ponderous bits in the middle, including one involving a flood on Carlos's farm, feel extraneous and slow down the narrative.

But there's no question that Robinson's vocals and musicianship, and Quijada's rap and beatboxing skills, along with both performers' charisma on the stage, make for a winning, eminently watchable combination.

The direction by Berkeley Rep Associate Artistic Director David Mendizábal is kinetic and fresh, and the junk-shop honky-tonk set design by Riw Rakkulchon is warm and visually rich, complete with multiple tiny screens that look like old cathode-ray-tube box monitors but become pieces of the projection design throughout by Rasean Davonte Johnson.

While Mexodus is, no doubt, a piece of theater with a history lesson baked in, it is a fresh, often moving, and wholly entertaining one that is a surefire crowd-pleaser to boot.

'Mexodus' plays through October 20 at Berkeley Rep. Find tickets here.