But one thing composer Richard Rodgers and librettist Oscar Hammerstein II, in their first collaboration, kept fairly traditional was the sound of the leading couple’s first duet: “People Will Say We’re in Love.” As originally written and performed, the bantering back-and-forth between the cowboy Curly and the ranch girl Laurey — a “list of don’ts” discreet lovers should live by — had the contours of old-fashioned operetta: coy, sweet, soaring.

Operetta was not what director Daniel Fish had in mind when he conceptualized a revival of the musical that would expose its underlying danger and violence. His production’s focus on Laurey — and how her romantic choices reflect a woman’s limited powers in her era and perhaps ours — put particular pressure on “People Will Say We’re in Love” to express those themes.

As such, sweet and coy weren’t going to cut it. If the operetta style made sense in 1943 as a way of suggesting the world of 1906, something earthier and more immediately accessible was needed to match Fish’s interpretation decades later. For a production emphasizing sex, deprivation and loneliness, the sound of country and bluegrass music was a logical choice.

But the marching orders from the Rodgers and Hammerstein Organization, which controls the way “Oklahoma!” can be produced, were to leave the essential elements of the songs alone, meaning no alteration of melodies, harmonies or rhythms. Not that anyone wanted to change them; they’re basically unimprovable.

So how did a lush throwback like “People Will Say We’re in Love” become the sexy, stripped-down, countrified number being sung in the current revival and on its just-released cast album?

Enter the production’s orchestrator and music supervisor, Daniel Kluger. He and the music director, Nathan Koci, along with a group of instrumentalists who have been with the project for years, sought to build a totally new sound world on the sturdy armature of Rodgers’ music.

“When one set of variables is fixed,” Kluger said, “others come into play.”

Here are four of those variables — or as Hammerstein almost put it, a list of do’s for you.

Instrumentation: The first musical difference you notice at the Circle in the Square Theater, where the revival is playing, is a visible one: The musicians aren’t in a pit but onstage with the actors, costumed as if for a hootenanny. There are also far fewer of them. Instead of the 28 players called for in Robert Russell Bennett’s original orchestrations — including 13 strings — there are now just seven, with no brass or woodwinds and only one violin, cello and bass.

The new instrumentation favors plucked and strummed sounds (like those made by banjo, mandolin and guitar) over smooth, legato sounds (like those made by clarinets, French horns and bowed violins). The overall effect is dry and spare instead of sweet and smooth.

So where the 1943 version has a full string section playing “arco” (with bows), the new version has the three string players playing pizzicato (with their fingertips), along with guitar, banjo and mandolin.

The attack suggests that the playful lyrics, in which Curly and Laurey accuse each other of overdoing their romantic gestures, will have a sharper edge than we’re used to. The plot bears that out, as the farmhand Jud Fry becomes dangerously fixated on Laurey. In this rendition, “People Will Say We’re in Love” is not just a love song in playful disguise, it’s a warning.

The new orchestration also connects the score to the prairie, with instruments ordinary people used to play in fiddle bands. The addition of a pedal steel guitar in Curly’s chorus, which he sings while strumming an acoustic guitar onstage, amps up the bluegrass sound with its twangy accent.

Key: In Rodgers’ manuscript both choruses of the song, one for Laurey and one for Curly, are notated in the key of C, probably because, with no flats or sharps, it’s the quickest way to get a draft down on paper. On the 1943 original cast recording and in the 1955 movie, Laurey sings hers a half-tone up, in D flat. (The published version is another half-tone up, in D.) Any of these keys puts the singer — Joan Roberts onstage, Shirley Jones in the movie — in a soprano sweet spot, with top notes that ring.

But for the current revival, Laurey’s chorus has been transposed down to the key of A, taking Rebecca Naomi Jones, who plays the role, into a smoky belt range that starts low and never gets above a C sharp. Without the high notes, and the ringing tone that comes with them, all traces of operetta are gone. There’s no more showing off for the audience or even for Curly; it’s as if Laurey has other things on her mind than making pretty sounds. She’s playful but worried.

The opposite effect is achieved when Curly’s verse is abruptly restored to D flat, letting him sing like the glib and happy cowboy he is, mostly unaware of the danger ahead.

Phrasing: For Roberts and for Alfred Drake, the original Curly, words like “bouquets,” “glow” and “grand” are opportunities for portamento: fainting falloffs from higher notes to lower ones. Because our ears today register such flourishes as operatic and old-fashioned, none are used in the current revival’s performances. Instead, Jones and Damon Daunno, as Curly, use country music tropes, including vertiginous pitch-bending, rhythmic stuttering and even cowboy-style yodeling to express desire, exuberance and the possibility of actual sex.

Fill and Frills: What is the orchestra doing while the singers catch their breath between phrases? It’s providing fills and frills: chattering woodwinds or swooping strings to keep the song afloat. Or at least it used to be. But in the revival’s orchestration, the fills are either plain and flinty, often led by a plucked violin, or removed entirely. What’s left is just the song’s harmonic skeleton: a bare-bones figure as arid as the prairie. That the sung melody is rarely “doubled” by an instrument in the orchestra enhances the feeling of isolation.

None of this is to say that “Oklahoma!” can never again be performed in the style Rodgers and Hammerstein originally imagined for it. The songs are capacious enough even to return to operetta someday.

Strong enough, too: Stripping them of the trappings of gorgeousness doesn’t denature them. It reminds you that “Oklahoma!” was groundbreaking not because it was so pretty. It was groundbreaking because that prettiness was built on an understanding of characters for whom even prettiness — even love — was a luxury.

This article originally appeared in The New York Times.