At the beginning of Paul Coates' new play, The End of It, currently playing at the Matrix Theatre, a long-married heterosexual couple living in Los Angeles, Joanna and Drew (Kelly Coffield Park and Coates), are recovering from a party they've just thrown. As any number of sociologists and dramatists from Erving Goffman to Samuel Beckett will tell you, it's not just sex or common interests that hold couples together. It's the repartee.

Joanna and Drew have their shtick down pat, in a style they've perfected over years. With a contempt ranging from withering to harsh, they ridicule and deride each of their party guests. Call it a joint assault that binds, or appears to, as though two people are one organism.

Moreover, they mock their so-called friends in a lingo that has a prescribed rhythm. It's an aural dance of overlapping and often unfinished sentences. Either the ends of the sentences go without saying or they're completed by the other spouse. Joanna and Drew have perfected a barb-tinged linguistic tango. It's sexual and sadistic.

It's also 1 a.m., and they're both weary in this opening scene. At one point, she's wandered offstage when he utters the words that will form the crux of the scenes to come: “I want a divorce.”

She doesn't hear him at first, but she will soon enough.

The play's larger conceit is that in the midst of the agony he's created for them, in the midst of their reckoning with the abrupt new reality of him wanting a new life and her not, their “script” will get taken over by a gay male couple (David Youse and William Franklin Barker) who are enduring an identical parallel schism, and then by a gay female couple (Ferrell Marshall and Wendy Radford).

Though it's not so, you'd think the play might have been written for one pair but three couples auditioned, and the director chose all three to do the same play, in order to apply various chemistries and circumstances to the same script.

The action unfolds within a 24-hour span, as the partner wanting the divorce is about to leave for a business trip to London. At points in the two-act play, well-acted under Nick DeGruccio's staging, all three couples occupy the stage, and one character will speak as though talking to one of the partners of a different couple, or as though talking to him- or herself. It's as though DeGruccio's directorial argument is that as the partnerships disintegrate, it doesn't really matter to whom the characters are talking.

The other point of the staging is that it almost doesn't matter who's breaking apart. The “break-up” scenario, and the repartee that accompanies it, contains shapes that are universal.

It's difficult to discern whether we're watching a definitive take on the art of uncoupling, or a soap opera, or both. The TV-familiar melodrama wears thin, while the play's more absorbing proposition floats alongside it: Regardless of the idiosyncratic personalities of the couples, the phases of divorce are as inexorable as cancer.

I'm not persuaded that's true, but as a proposition it's worth considering, and it makes The End of It worth watching.

No living playwright knows more about repartee and the way it informs a relationship than Neil Simon. His comedies The Odd Couple and The Sunshine Boys are monuments to figurative marriages on the brink of divorce, of people who drive each other nuts, and they do so in the ever-so-carefully constructed rhythms of Borscht Belt humor.

The Sunshine Boys, written in 1972 and now in a revival at the Ahmanson, isn't just about an odd couple. It's as much about the theater and its legacy. A washed-up vaudeville team, Al Lewis and Willie Clark (Justin Hirsch and Danny DeVito), can't seem to live with or without each other. When the play begins, they're divorced, having broken up years ago after their act bombed one night and Al announced his retirement as abruptly as Drew tells Joanna “I want a divorce” after 20 years of marriage, in The End of It.

“When he retired himself, he retired me,” Willie explains to his nephew (Justin Bartha), a talent agent who's trying to get the pair to reunite on a TV special.

Like so many comedy teams, from Abbott & Costello to the Smothers Brothers, they're a single organism with a humor that derives from their interactions as much as from their jokes. DeVito and Hirsch have reunited for the first time since their joint appearances on the sitcom Taxi, which started on ABC in 1978 and concluded its run in 1983 on NBC. Their reunion is a perfect fit for Simon's play, adding a layer of sweet irony to this delightful production.

The stocky, bald DeVito stands at 5 feet, and sports maroon and gold, vertical-striped pajamas and thick glasses, shadow­boxing with quips through most of the play. This is contrasted against Hirsch's looming, world-weary elegance.

The primary scenes contain a rehearsal — taking place in Willie's tatty apartment — for the duo's reunion, which eventually involves the taping of one of their routines at a TV studio.

Yet their interaction when Willie finally agrees to do the show is as much of a vaudeville routine as the show itself.

Al, who now lives in New Jersey, hasn't been in New York for some time.

Willie asks him how he now finds New York.

“My daughter drove me,” Al shoots back, deadpan.

Then, when the repartee breaks down, there's the physical comedy of their preparing the set for their rehearsal. As they each move and re-move tables and chairs, each of them slowly, obliviously undoes what his partner has just set.

This is a gorgeously orchestrated and tender farce under Thea Sharrock's direction.

The sketch itself, about a masochistic doctor, contains Borscht Belt staples, such as the squeaky-voiced nurse (Annie Abrams) with huge breasts and a bottom to match. Her protruding derriere, as she leans over the doctor's desk, is at the same altitude as DeVito's gawking face, even when they're standing at the same level.

The skit has the wonder of being both lame and entrancing at the same time, the same wonder that defined so many sketches on The Carol Burnett Show, with Burnett and Harvey Korman.

The humor of an era is a window onto who we were and, inevitably, who we've become. This is among the benefits of seeing The Sunshine Boys revived. Some of the play's humor comes from turn-of-the-last century theater, to which Boys offers its homage, but most of it comes from two decades starting in 1950, when Simon was in his prime. He started his career in radio, which is why the beauty of his plays comes from the repartee.

In The Sunshine Boys and The End of It, when the repartee loses its rhythm, so do the marriages contained in the plays.

THE SUNSHINE BOYS | By Neil Simon | Presented by Center Theatre Group at the Ahmanson Theatre, 135 N. Grand Ave., Downtown | Tues.-Sat., 8 p.m.; Sat., 2 p.m.; Sun., 1 & 6:30 p.m. (added perfs Thurs., Oct. 24 & 31 , 2 p.m.); through Oct. 31 | (213) 628-2772 |

THE END OF IT | By Paul Coates | A guest production at the Matrix Theatre, 7657 Melrose Ave., Fairfax District | Thurs.-Sat., 8 p.m.; Sun., 5 p.m.; through Oct. 20 | (323) 852-1445 |

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