Carnival of Soul

Clap your hands, everybody, and sing along with Pol! That’s as in Pol Pot, the leader of the genocidal Khmer Rouge regime in Cambodia, which wiped out nearly a quarter of that country’s population during the second half of the 1970s.

All right, to be exact, it’s not Pol himself who’s shaking a tambourine and urging the audience to get up and dance at the Pershing Square Signature Center, where Lauren Yee’s adventurous, tonally scrambled “Cambodian Rock Band” opened on Monday night. Instead, this enthusiastic master of ceremonies is called Duch. That is the nom de guerre of the former math teacher Kang Kek Iew, a Pol confederate known as “Cambodia’s Himmler,” who ran the notorious S21 prison (read: death) camp.

The real Duch, who was the first of the Khmer Rouge leaders to be tried for mass murder, is now serving out a life prison sentence. But Yee, a playwright of great heart and audacity to match, has seen fit to give her version of Duch the run of her brash but conventionally sentimental play, which features the songs of the Los Angeles-based Cambodian surf rock group Dengue Fever.

Duch is bravely portrayed by Francis Jue with a flaming archness that neither he nor Chay Yew’s production can quite pull off. Think of him as a combination of the creepy Weimar-era M.C. from “Cabaret” and the antic Hitler from the recent Oscar nominee “Jojo Rabbit,” and you’ll understand that Jue’s assignment is not an easy one.

“Genocide, genocide, genocide — boo!” Duch says, taunting us with a full dose of snark, in his opening monologue. He proceeds to ask us, with justification, “Are you confused? Welcome to Cambodia, 2008!”

That’s the year in which Duch’s trial begins. And in Yee’s fictionalized evocation of that time, Neary (an earnest Courtney Reed) — a young American NGO worker of Cambodian descent — has stumbled upon crucial evidence. It was thought that only seven people had survived their time in S21. But Neary has unearthed a photograph the suggests there may have been an eighth.

And who might he or she be? Oh, dear. This is where the Code of the Spoilers dictates that I become evasive. But it’s pretty much impossible to discuss this play without disclosing its essential plot twist, which, after all, is revealed fairly early.

The eighth survivor is a man who, hearing of Neary’s involvement in the case, has come to visit her in Phnom Penh. His name is Chum (Joe Ngo), and he is Neary’s father.

Cloaked in a camouflage of hard-smiling passive aggression, Chum has always been reticent with his family on the subject of his life before coming to America. However, the demands of international justice and an insistent daughter force him into memoir mode, which means propelling the play into a sustained flashback, set in the Khmer Rouge era of the 1970s.

I’m making “Cambodian Rock Band” sound more straightforward than it is. It is structured, a bit haphazardly, as a nest of frames within frames.

It is as if Yee, whose earlier works include the similarly ambitious time-traveling play “The Great Leap” (set partly in China), feels that a subject as monstrous as the Khmer Rouge cannot be approached head-on. So she tugs us, by degrees, into the horror at her play’s center with bait-and-switch tactics, which include sitcom coziness, cheerfully packaged shock effects (including dark commentary by Duch) and good old rock ’n’ roll, Cambodian-style.

Takeshi Kata’s mutable set is dominated by a bandstand, and the show begins with a performance by the Cyclos, the fictional group of the title who here perform the Dengue Fever’s music. The songs — a bright, raucous confluence of varied international pop strains — are agreeably performed by Abraham Kim, Jane Lui and Moses Villarama (who doubles in the role of Courtney’s boyfriend), as well as Reed and Ngo.

The Cyclos are not here just for our listening pleasure. They will turn out to be a pre-revolutionary Cambodian combo of which Chum was a member. Their band bears weighty significance in terms of both plot and theme. “In case you were not aware,” Duch informs us, “music is the soul of Cambodia.” It will also become an early casualty of the Khmer Rouge.

To Yee’s credit, she neatly connects all the seemingly far-flung dots of her story. But neither her script nor Yew’s production — which features period-defining costumes by Linda Cho and lighting by David Weiner — can comfortably reconcile the radical shifts in style and mood, between the bright sardonicism of Duch’s speeches to the audience and the furrowed-brow sincerity of the father-daughter scenes.

This is a shame. For there is indeed a compelling heart of darkness in “Cambodian Rock Band,” explored in a long, second-act sequence set at the S21 Prison and performed unflinchingly by Jue, Villarama and Ngo.

In these scenes, Ngo’s Chum sheds his middle-aged mantle of strained affability to become a raw, quivering soul whose raison d’être is to exist, no matter the cost. And Yee’s adroit use here of the characters’ real names and assumed names becomes a heartbreaking reminder of how what we think of as a fixed human identity can melt into pulp under inhuman conditions.

Cambodian Rock Band

Tickets Through March 15 at the Pershing Square Signature Center, Manhattan; 212-244-7529, signaturetheatre.org. Running time: 2 hours 25 minutes.