NEW YORK » Something rare and wonderful happened at the opening night of the Encores! concert production of "Gentlemen Prefer Blondes" at City Center this month. At the end of the show, when the performers took their bows, the audience remained seated.

Let me hasten to add that there was no doubt that this audience had enjoyed mightily what it had just seen, a succession of showstoppers that climaxed with a knockout rendition of "Diamonds Are a Girl’s Best Friend," that immortal anthem to nonliquid assets. The number was sung by Megan Hilty, who gave the gold-digging Lorelei Lee character an original comic audacity that erased memories of Hilty’s most famous predecessors in that role, Carol Channing and Marilyn Monroe. It felt like one of those single, golden nights, so cherished by theatergoers, that thrust its leading lady into the firmament of musical stardom.

And at the final curtain, we stayed in our seats. We whooped, we roared, we beat our hands raw with clapping. But no one, as far as I could see, was standing up. "Gentlemen Prefer Blondes" had been accorded the five-star tribute of a sitting ovation.

I would like to make the case, officially and urgently, for the return of the sitting ovation. Because we really have reached the point at which a standing ovation doesn’t mean a thing. Pretty much every show you attend on Broadway these days ends with people jumping to their feet and beating their flippers together like captive sea lions when the zookeeper arrives with a bucket of fish. This is true even for doomed stinkers that find the casts taking their curtain calls with the pale, hopeless mien of patients who have just received a terminal diagnosis.

The SO (if I may so refer to a phenomenon that no longer warrants the respect of its full name) has become a reflexive social gesture, like shaking hands with the host at the end of a party.

Or, to put it in cruder and more extreme terms, it’s like having sex with someone on the first date, whether you like the person or not, because you think it’s expected.

The reasons for the ubiquity of the promiscuous SO have been widely pondered by cultural pundits. One theory has it that it’s because habitual theatergoers have become a relative rarity. Many who attend big Broadway shows are tourists whose itinerary includes, along with visits to the Statue of Liberty and the Hard Rock Cafe, a performance of "Wicked" or "Jersey Boys."

For such audience members, standing to applaud at the end of a show has become part of the Official Broadway Experience. And if you’ve spent several hundred dollars for that pair of orchestra seats, an SO seems to help confirm that the money wasn’t wasted.

I also have a suspicion that for some people, standing immediately at the end of the show is simply a physical relief after an hour or more of immobility. Besides, the sooner you’re on your feet, the greater your odds are for beating the crowd to the exits. And, oh yes, let’s not discount the domino effect of an SO: Once the person in front of you is standing, you too must stand if you want to see what’s on stage.

In London, where theater remains a larger and more natural part of the general cultural conversation, the SO is less epidemic. Although I have felt its sweaty presence at some of the bigger West End musicals (often imported from Broadway, so perhaps they arrived carrying the virus), I can’t remember the last time I witnessed an SO at the National Theater, where the level of professional quality is consistently and rewardingly high.

Admittedly, some shows deserve an SO, which I don’t necessarily mean as a compliment. "Newsies the Musical," in which the characters keep dancing and cartwheeling and jumping all over the place, seems so pathetically eager for an SO that to deny it one would be like forbidding an adorable puppy its chew toy. Similarly, Liza Minnelli — whenever and wherever she appears — must receive an SO. It’s part of the unwritten but unbreakable contract between her and her audience (as it was with her mother, Judy Garland).

And then there are — or once were, the old ones tell us — the meaningful SO’s. These were not instantaneous or knee-jerk. Legend has it that on the opening night of Arthur Miller’s "Death of a Salesman," the audience was so moved by what it had witnessed that it sat in shocked silence, collecting itself and drying its tears, before the applause broke out.

People seeing Mike Nichols’ current revival of that play may well be similarly moved by the tragedy of Willy Loman, its title character. But at the performance I attended, they were on their feet in a megasecond, as if electrodes had been applied to their legs.

So I can’t tell you how heartened I was, at the end of a packed spring theater season, to be part of that seated ovation at "Gentlemen Prefer Blondes." I should point out that among audiences for musicals, those who attend the Encores! productions are probably the most sophisticated and discriminating in town. Many know the history, in detail, of the show they’re seeing and the resumes of those appearing in it.

Can’t we all, please, strive to be a little more like them? I’m not asking for the wholesale abolition of the SO. That would be a sadly quixotic demand. I’m just asking you, my comrades in urban theatergoing, to think before you stand, if you must stand at all. And to remember, in an age in which the SO is as common in a Broadway theater as an endless line for the ladies’ room at intermission, that staying seated has become the exceptional tribute.

© 2012 The New York Times Company