If anything characterizes the fashions of pop and youth culture, it's that they are always, in Carly Simon's words, coming around again. Like Nietzsche's "eternal return of the same," any movement—from rockabilly to heavy metal, electronica to soul—that attracted followers the first time round eventually gets rediscovered and revived, often several times.

PRETTY THINGS: 'John Rothermel in a Fashion Pose (Cockette)' (1973) by Peter Hujar, at Tate Liverpool The Peter Hujar Archive, LLC; courtesy of Pace/MacGill Gallery, New York

One, however, has never been revived, and has been almost universally reviled since its heyday: glam rock. It's not hard to see why. Even teenagers, with their boundless enthusiasm for looking ridiculous, have to draw the line somewhere, and the artificial fabrics and science-fiction design of glam rock's outfits, which make the costumes in the closing credits of "Mamma Mia!" look understated, are some way beyond that limit.

As for the music, while prominent exponents like David Bowie and Roxy Music became highly influential and credible, they left glam behind. Yet songs by bands like Slade, T-Rex, Sweet and Wizzard never quite went away—at least in the U.K., birthplace and stronghold of the form.

Though staples of the pub jukebox and the office Christmas party, they were rather guilty pleasures. With their foot-stomping basslines and too-catchy choruses, they were for singing along to after too much to drink, rather than anything to be taken seriously.

Suddenly, however, glam is back in the spotlight. The Liverpool Tate gallery has mounted an exhibition devoted to the form, drawing hitherto unsuspected connections between it and the work of artists like David Hockney and Andy Warhol (about whom Mr. Bowie wrote a song). Mr. Bowie himself is the subject of a show at the V&A, which will include some of the singer's stage costumes from his Ziggy Stardust incarnation.

This renewed attention makes several things apparent. The first is that much of the music is better crafted than its reputation suggests—but also much more tied to the conventions of pop and rock 'n' roll. The difference is almost all performative; it's in how these songs were presented.

The second is that, as so often with youth fashions that outraged parents of the time, nostalgia and hindsight render what seemed threateningly lascivious and dangerously rebellious almost innocent.

Nostalgia and hindsight render what seemed threateningly lascivious and dangerously rebellious almost innocent.

Now that all the young dudes whom Mott the Hoople hymned are old news, David Bowie's pretty things, driving their mamas and papas insane, don't look so much like "the start of the coming race." They're more like something recognizably in the tradition of vaudeville, a line that runs from pantomime through to Alice Cooper (still cheerfully hamming it up, aged 65).

There is, though, one feature of glam rock—not unrelated to the innuendo of those traditional entertainments—which proved revolutionary. The youth culture of the 1960s may have promoted sexual license, but glam rock was the first mainstream pop movement to trade on androgyny and sexual ambiguity.

What outraged parents four decades ago wasn't the music, but Marc Bolan's makeup and Mr. Bowie's flaunted bisexuality.

Today's general tolerance of different sexual preferences may owe more than we realized to preposterous outfits, hair glitter and catchy three-chord tunes. Perhaps the greatest mark of glam rock's influence is the fact that most of the public think these transgressive statements now look rather quaint. Civilization didn't crumble; it was all just a bit of fun.