Sex sells, of course, now and forevermore. That much is a mortal lock. But if prurience intrigues us, we also have a very complicated history and relationship with what stokes the fires down below — one inextricably intertwined with the times in which we live, no matter the individual moral shading of our sexual compass. With this in mind, there’s plenty to titillate the top brain while watching the new documentary American Swing, a go-go snapshot of partner-swapping and anonymous group sex in New York City felled by, among other things, the burgeoning AIDS crisis of the 1980s.

The year was 1977, and even as New York hurtled into bankruptcy, the city’s nightlife hit unprecedented heights. In midtown, the ultra-exclusive Studio 54 was a cocaine-fueled celebrity playhouse. Downtown, at the spartan CBGB’s, punk rockers set out to thrash and destroy pop music’s status quo. Meanwhile, in the basement of the prestigious Ansonia building on the conservative Upper West Side, Plato’s Retreat opened its doors to ordinary couples who came to dance, swim, enjoy a terrible buffet and, oh yeah, swap sexual partners.

The brainchild of former wholesale meat purveyor Larry Levenson, Plato’s Retreat quickly emerged as the epicenter of public sex for the “me” generation, coming several years on the heels of the breakthrough mainstream success — fueled in large part by long runs in Times Square — of porn flick Deep Throat. Previously, swinging was mostly an underground activity, engaged in primarily by the attractive and well-to-do. But Plato’s welcomed anyone and everyone; it was a “poor man’s Playboy Mansion,” as one interviewee recalls, where it didn’t so much matter the size or shape of your body. For a mere $25 to $35, couples checked their pedigrees and judgments at the door. At this clothing-optional Disneyland, debutantes got it on next to bus drivers, and Wall Street movers and shakers gave secretaries the “starlet treatment.” For Levenson and others, Plato’s was utopia; for some, it’s a time capsule they’re eager to forget. Utilizing exclusive interviews with former patrons, employees and family members, and intercut with never-before-seen archival materials, American Swing brings this epicenter of sex and excess to the big screen.

If only it did it better. Co-directed by Matthew Kaufman and Jon Hart, and based on an article by veteran journalist Hart, American Swing is undeniably engrossing, insofar as sex is inherently interesting, and the notion of serial, strings-free couplings even more so. Unfortunately, despite the exhaustiveness of their efforts in tracking down some of the key players in the story of the club, the filmmakers have less success in constructing a cogent, contextualized narrative about the rise and fall in popularity of Plato’s Retreat, let alone an insightful examination of its founder. Certain subjects are identified only by their first names, and at times it’s not immediately clear, with the editorial cross-cutting, if they’re talking about one another or their experiences in general. The film isn’t helped by the fact that Levenson’s voice is silenced (he passed away of heart illness in 1999, though appears liberally in clips from Donahue and other talk shows), but it further does itself no favors in its handling of interviews with surviving family members, like his first wife, and sons. The movie’s press notes make mention of hundreds of hours of interviews between Hart and Levenson, spanning years, up until his death, and it also references Levenson’s estrangement from his sons. But, astonishingly, the film doesn’t include this material, or even Hart’s refracted thoughts on the curious fall of this brash character. Everything about American Swing is only thumbnail-deep, from its intimations of Mafia investment to the true nature of Levenson’s relationship with his longtime girlfriend and Plato’s Retreat co-owner.

Thankfully, there are more than a few moments of piercing, smirky humor, as when writer Buck Henry speculates on the value of post-coital dialogue between people who’ve just met, and another former patron remembers “women talking and trying to figure out about carpooling to Hebrew school in the morning.” (Robin Leach just came “to look,” one former worker notes, while Abbie Hoffman failed to get laid.) Most of the more lurid, vivid descriptions of reminiscence pertain to the “mattress room” (above), a sexual-free-for-all zone which one interviewee likens to a writhing bucket full of worms.

Photographer Donna Ferrato, meanwhile, recounts an amazing (apocryphal?) anecdote about swimming under arcs of male ejaculate, and notes that the mattress room was “terribly exciting, but also depressing, because it kills any notion or sense of romance you might have.” It’s just that level of substantive emotional analysis that the film is most missing. As a curious artifact of the sexual revolution, Plato’s Retreat has plenty of intrigue, both for older audiences who — wistfully or otherwise — missed out on the experience firsthand, and younger audiences now grappling with the sensibility and repercussions of ever texting naughty photos of themselves. American Swing captures a bit of that glossy surface engagement, but it doesn’t have, ahem, the rigorous thrust necessary to leave a lasting impression. (Magnolia, 81 minutes, unrated)