Oh, that every dark comedy to come down the pike was as playful as “Woman at War.”

It plays around with expectations, setting us up and tripping us — time and again.

It toys with conventions and worn comic tropes — identical twins, mistaken identity, running gags.

And Benedikt Erlingsson’s Icelandic caper comedy has fun with music, installing an offbeat trio (tuba, drums and accordion or piano or organ) who score the movie, live on set, standing behind our “Woman at War” as her odyssey is by turns serious, possibly tragic or — more often — just plain strange and whimsical.

When Halla finds out her adoption of a Ukrainian orphan might come through, a Ukrainian trio — in native garb — shows up, her very own Greek Chorus, an ironic commentary on Halla’s newly-complicated plight, singing in Ukrainian.

In “Woman at War,” Halla (Halldóra Geirharðsdóttir) is quintessentially “quixotic.” But unlike Don Quixote, famed tilter at windmills, this 50ish chorus director is tilting at power line pylons. Halla is an Icelander at war with the government’s high-handed plans to bring more work to the nation’s polluting smelting industry — “Chinese money” and all. Her way of fighting it? Take down the power lines that keep the metals and ores melting.

We meet Halla in full warrior princess mode. She’s hiked out across the lava fields that form Iceland’s terrain, brought her bow and arrows and has shot a cable across the power lines, shorting out the works.

When the black helicopter pops up to track her down, she’s resourceful enough to get away, but only as far as the nearest farm.

“If you want to help me, it has to be now.”

Her pitch, that this, her fifth act of sabotage, does not make her a criminal, that “I’m trying to stop crimes against us,” is unnecessary. The farmer (Jóhann Sigurðarson) figures they’re cousins, not a far-fetched guess on the tiny rock on the edge of the Arctic Ocean.

Halla has just made her first getaway, a skin-of-her-teeth escape back to her solitary life of bike-commuting to work, leading a chorale, maintaining contact with her government “mole” who updates her on the whole smelting conspiracy and covering her tracks as she single-handedly throws a spanner into the works.

Her latest sabotage has netted a suspect, a convenient Spanish tourist (Juan Camillo Roman Estrada) who becomes a running gag, always in the wrong place at precisely the wrong time. The cops jail him and let him go, but not without a jaunty “Welcome to Iceland!” — one of the few times anybody here speaks English.

Co-writer/director Erlingsson (He did “Of Horses and Men.”) loses himself in Halla’s cunning and resourcefulness. She’s not just handy with a bow and arrow. She knows she’s risking electrocution, messing with high tension lines. She’s got her rubber gloves.

And she’s careful in other ways, too — right on the edge of paranoid. Seriously, how easy would it be to catch an eco-terrorist on a remote island with only 350,000 people on it — especially an island with the omnipresent CCTV “security cameras” popping up in every corner of Reykjavik?

Erlingsson has her raise an eyebrow at questions Halla’s asked about the getaway car she parked on the street. The questioner is blond, wearing black, his eyes hidden behind Ray Bans. It’s only a moment or two later than she and we see he’s pushing a stroller. NOT a cop.

She wants to get her message out to the public, and when cutting up newspapers to create a lengthy “ransom note” styled “manifesto” proves impractical — she needs a typewriter, untraceable, preferably. Check out the way Halla procures it and then distributes her “message.”

Through it all, Geirharðsdóttir gives Halla this inscrutable poker face — until, that is, she gets the news that her long-ago filed-for adoption (a Ukrainian war orphan) has come through. She lets us see the shock, and later the delight that this news — in the middle of all the drama she’s filled her life with — gives her.

The deadpan whimsy spills out of many scenes in this “War” film. Halla’s farmer “cousin” lives alone with his sheep dog. He’s named the dog “Woman.” As in “Woman, STAY.” “Woman! BARK!” “SHUT UP Woman!”

But I can’t say enough about the way Davíð Þór Jónsson’s music and musicians are incorporated into “Woman at War,” setting the picture’s tone, having fun with scoring the film and providing visual/musical commentary to Halla’s adventures.

It’s not just that the simple rhythms — a snare drum march in some scenes, a folkish accordion or oomphs from a tuba in others — that tickle. We see the percussionist impatiently clicking his sticks together behind Halla as she reasons through her next plot and watch the ensemble perform as she sprints by, running from drones or police helicopters.

When Halla faces a decision, she makes eye contact with this or that performer before she — and they — decide what course she is taking, by virtue of the music that the performer scores it with.

When you see the source producing music in a scene in a movie, that’s called “diegetic sound.” Several movies have played around with this, but “Woman at War” has the best diegetic placement of music and musicians in a story since “There’s Something About Mary.” It’s just delightful.

Erlingsson takes a fairly cut-and-dried caper comedy and tosses twist after twist into it, letting “Woman at War” surprise us just as often as it repeats a running gag (the poor, cursing bicycle-camping Spaniard).

And as predictable as this might have been and sometimes is, Erlingsson and his stoic, poker-faced star save the best twists for the finale, letting this genial lope across the lava flows finish with a flourish and leave you with a big grin.

MPAA Rating: unrated, locker room nudity

Cast: Halldóra Geirharðsdóttir, Jóhann Sigurðarson, Juan Camillo Roman Estrada, Jörundur Ragnarsson

Credits: Directed by Benedikt Erlingsson, script by  Ólafur Egilsson, Benedikt Erlingsson. A Magnolia release.

Running time: 1:40