The R-rated romantic comedy always teeters between vulgarity and sentimentality, and usually collapses into the arms of the latter before the final credits. A Good Old Fashioned Orgy sounds like more of the same — and it is. But the movie keeps its balance better than its leering title might suggest.

The movie opens in Manhattan, where Eric (Jason Sudeikis) and his circle of longtime friends work. But writer-directors Peter Huyck and Alex Gregory don’t think most of their jobs are worth a mention, and the story quickly relocates to the Hamptons. That’s where Eric’s father (Don Johnson) owns a beach house his son uses to host boisterous theme parties.

After a “White Trash Bash” that draws a first-timer — sexy local real estate agent Kelly (Leslie Bibb) — dad makes his lone appearance to announce that he’s selling the house. (Naturally, Kelly’s on the sales team.) Bereft, Eric and pudgy sidekick Mike (Tyler Labine) ponder the perfect farewell party. Rather than one of their customary cast-of-hundreds benders, they decide on an intimate little orgy with only their closest pals. Conveniently, half of them are female.

The incongruous gang includes seemingly mature therapist Alison (Lake Bell) and hypochondriac financier Adam (Nick Kroll), as well as indecisive rocker Duquez (Martin Starr) and his groupie/girlfriend Willow (Angela Sarafyan). Even less defined as characters are Sue (Michelle Borth) and Laura (Lindsay Sloane). Pointedly excluded from the party are Glenn and Kate (Will Forte and Lucy Punch), because they’re about to get married.

Briefed on the plan, everyone but Mike rejects the orgy idea, despite Eric’s speech about how AIDS deprived their generation of the erotic experimentation their parents supposedly enjoyed. “We’re the lamest generation!” he proclaims, with the mock earnestness that was once Bill Murray’s trademark.

But the potential orgiers all gradually change their minds, for various reasons. Two examples: Sue decides this is her chance to get into bed with Eric, her longtime secret crush. And Alison needs to declare her independence after splitting with her controlling Euro boyfriend (Rhys Coiro).

It’s hardly a surprise that most of the simulated onscreen sex doesn’t involve Eric and his friends. It occurs instead during a swing-club session that Eric and Mike attend, looking for tips rather than action. (Many of the swingers seem to be in their 50s and 60s, which should send the intended chills down the spines of the movie’s Gen-Y viewers.)

If the comedy feels generic, that’s partially because of the cast. In his short movie career, Sudeikis has already worn out the role of smooth-talking but weak-chinned babe magnet. (See, for example, Horrible Bosses.) And while Labine and Kroll aren’t well-known, their models are: The former’s slacker diction sounds eerily like Jack Black’s, and the latter’s shrill neurotic shtick is rebottled Jeff Goldblum.

Still, A Good Old Fashioned Orgy deserves credit for not entirely wimping out. The friends-with-one-time-benefits plot leads, of course, to several outbreaks of true love. But when the designated hump day arrives, Huyck and Gregory don’t run screaming from the house. They just place the cameras very carefully, so that little more skin is on display than in a ’60s beach-party flick. That’s sort of lame — but an unexpectedly well-sustained script saves this movie from being the lamest.

Copyright 2011 National Public Radio.