The unlikely product of the partnership between cinematic breast-fetishist Russ Meyer and Pulitzer Prize-winning film critic Roger Ebert, Beyond the Valley of the Dolls started life as a sequel to Valley of the Dolls (1967), but ended up as one of the great camp films of all time, bearing no relation to its source material.

The setup is simple: It’s 1969 and The Kelly Affair, a rock band comprised of three wide-eyed young women from the midwest, heads West with their manager to Los Angeles, where drugs, decadence, sex, and the record business all work to tear them apart.

From that simple premise, all hell breaks loose. There’s loud rock music, sex, wild parties, nudity, bad record deals, unwanted pregnancies, lesbianism, more loud rock music, more sex, more nudity, a crazy gender reveal, another wild party, etc. At the end, a lesson is learned.

Prior to this film, Meyer had a reputation in Hollywood, just not a very good one. An exploitation auteur, his films featured large-breasted women committing acts both violent and sexual in films with titles like Faster, Pussycat! Kill! Kill!, Mondo Topless, Wild Gals of the Naked West, and Europe in the Raw. So he didn’t get a lot of meetings at the major studios, at least until Vixen!, the first film given an X for sexual content, made a bunch of money. Then Fox came a-calling, hoping Meyer could save a languishing property, crank it out cheap, and “make an R film smashing against an X rating.” That’s what he and Ebert did.

According to Ebert, Meyer pursued a young audience with a specific formula: “There had to be music, mod clothes, black characters, violence, romantic love, soap opera situations, behind-the-scenes intrigue, fantastic sets, lesbians, orgies, drugs and (eventually) an ending that tied everything together… [the film would] simultaneously be a satire, a serious melodrama, a rock musical, a comedy, a violent exploitation picture, a skin flick, and a moralistic expose.”

The movie’s “curious tone” (Ebert’s words) come from Meyer’s very serious direction of the young unknown actors, who were afraid to ask whether or not they were making a comedy. Wild characters abound, but no one comes close to Ronnie “Z-Man” Bartell, the wild-partying madman (supposedly based on Phil Spector) who, in Paul LaZar’s astonishing performance, lights up every scene he’s in with a frenetic energy. What do they make Oscars for if this guy doesn’t get a nomination?

Candy-colored, oversexed and loudly amplified, with all sorts of contradictory messages lurking in its vision of decadence, Beyond the Valley of the Dolls is a masterpiece of its kind. No wonder Ebert never wrote another script.