Time was, it was easy to tell the good girls from the bad on MTV, The bad girls were the ones who danced real well, had their lingerie custom made and got hosed down in tantalizing slow motion; the good girls stayed home and watched it on TV. As Madonna went, navel and all, so went the girls of pop’s superficial end.

But lately that’s changed. “Truth or Dare” be hanged, good girls are making a comeback. Amy Grant, who has sold more than 10 million copies of her Christian-oriented albums, recently landed a No. 1 pop single with her infectiously clean “Baby Baby.” Wilson Phillips, a dauntingly wholesome trio comprised of the daughters of less-than-wholesome pop fathers Brian Wilson and Papa John Phillips, have been near the top of the charts for almost a year, singing sweetly about relationships and other proprieties. (When the three sing, on a recent No. 1 hit, “I want to be impulsive,” only a mother superior would worry that they might actually do it.) And Gloria Estefan, whose 1990 bus accident rendered her not only good but darn near a saint, has become so popular she doesn’t even bother crediting the Miami Sound Machine on her album titles anymore. Her “Into the Light” album, her first since the accident, sold a million copies in its first 10 days of release. Offering shallow wholesomeness in the place of shallow sensuality, the good girls have made innocence a hot pop commodity.

They are a throwback to a less brassy age-specifically, to the pre-Milli Vanilli days, before dance music got too big for many people’s britches. Dance music, with its easy pleasures and caricatured sexuality, is surely the devil’s playground. The good girls bring back traditional songwriting and instruments, as well as traditional values. They represent the latest frontier of ’90s multiculturalism: aggressively square white women making music that’s one step out of the elevator. It is only a sign of their sincerity that, after the aging heavy-metal guys and maybe Suzanne Vega, they are the worst dancers on MTV.

Like any marketing construct, good girls aren’t born, they’re made-sometimes by executive decision, sometimes by default. When Wilson Phillips first formed in earnest in 1986, according to Carnie Wilson, “Our producer wanted us to do dance music, but we tried it and we sounded really dumb.” While the trio, not being sufficiently liquid of hip or moist of lip, thus escaped pop’s Sodom and Gomorrah, former cheerleader Paula Abdul headed straight for the esthetic gutter her corporate benefactors picked out for her. “It was a very conscious decision on my first project to incorporate dance music,” said Abdul, who often seems like a good girl in bad girl’s bustiers. After selling 12 million albums as a pop tart, Abdul is now working on her good-girl credentials. “Rush Rush,” her new single, is a romantic ballad of high moral bearing.

One irony is that rock video, an overtly sexual medium, actually pushes the good girls forward, because it features so many interchangeable dancing vixens in secondary roles, usually in videos of male acts. In the age of raging Madonnas, sometimes being plain is the best way of being noticed.

J. L.

Of course, bad girls haven’t exactly rolled over. .. but maybe that’s a bad choice of words. At any rate, for all the progress of good girls, MTV’s two favorite passions remain the environment and young women in exotic undergarments. And after Madonna, no one is pushing the undergarment envelope as hard as Christina Amphlett of the Australian band Divinyls, whose hit, “I Touch Myself,” raises pop vulgarity to a new low. It’s a dilly.

Armed with enough fishnet for the Eastern Seaboard and a double-entendre subtle enough for “Wrestlemania,” Amphlett delivers the most touching paean to female masturbation since Cyndi Lauper’s “She Bop.” On the album cover to “Divinyls,” she demonstrates her technique. When it comes to smut, Amphlett is obsessed (though in a recent interview she admitted, “All the fishnet I’ve been wearing leaves me covered with dents”; this, surely, is the price of a leggy walk on the wild side). Yet as with Madonna’s “Justify My Love,” the explicitness of “I Touch Myself” hasn’t relegated it to the back rooms. The song is a mainstream hit, and possibly a taste of rock’s future. In a recent feature on the changing shape of pop radio, Billboard magazine devoted a section to the song; it was titled AUTOEROTICISM AS A FORCE FOR CHANGE. For years, Amphlett dressed up her sexuality in the ironic outfit of a schoolgirl, but to little American success. Now, in fishnets, she has finally found her audience. Probably the old approach was too subtle.