NEW YORK -- "Spring Awakening" has a title that is doubly or triply right. It refers first to the content of this explosive and engaging rock musical, but even though more than a century old, it also describes its effect on wintertime Broadway.

Those meanings were there at the start. When German playwright Frank Wedekind (1864-1918) wrote "Spring Awakening" in 1891, it was primarily shocking for its acknowledgment of adolescent sexuality and indictment of adult hypocrisy and repression. But it also broke ground aesthetically, going beyond naturalism (still fighting for acceptance itself) to presage expressionism.

Today, the effects are reversed. The young characters still experience their awakening spring of sexual experimentation, and the frank sexuality of a couple of scenes might still surprise some, but in general we're more used to that on stage. We're also used to attacking adult hypocrisy, although in the hands of Wedekind and adaptor Steven Sater, it still has the power to shock and disgust.

But as a musical, it's the aesthetic upheaval that feels like the real spring thaw, like the sudden torrent of water when a frozen lake loosens and crashes through toward the sea.

That torrent is in the combination of youthful, rawly powerful performers and Duncan Sheik's rock score, which has the rebellious joy of youth. The music has contemporary, in-your-face urgency, which, alternating with period scenes set firmly in 1890s Germany, creates a whiplash of emotional intensity.

You might think that the one would undercut the other, but they don't, thanks to director Michael Mayer, creators Sater and Sheik and the completely engaging cast. The repressed period feel of scenes adapted pretty directly from the original German feed a desperate seriousness into the rock break-outs, while the songs translate that period despair into contemporary protest and send us back into the story with our senses tingling, more alert to what might otherwise seem musty or antique.

But to be fair to Wedekind, much of the effect of this "Spring Awakening" is precisely that of his play, which in the several times I've seen it (it's a favorite of college groups) has continued both to charm and alarm. The rock score intervention mainly heightens what's always been there.

Not that most of the excited audience cares a whit for Wedekind. Not since "Rent" have I felt so much youthful drive and energy on Broadway, whether onstage, in the audience or even post-show at the stage door, where the cast, Jonathan Groff and John Gallagher Jr. especially, are squealed over like rock stars.

The story concerns a group of students in a repressive, competitive secondary school. We focus on Moritz (Gallagher), who's marked for failure and tormented by hormonal urges he doesn't understand; his good friend, the handsome, successful Melchior (Groff), who knows a little more; and Wendla (Lea Michele), a sweet, emotional girl left in perilous ignorance by her terrified mother.

Sater doesn't take Wedekind entirely as he found him. Aside from tightening the story, he also changes the final scene so that Moritz and Wendla sing Melchior into the future, rather than the creepier, more pessimistic version of Wedekind. He also excises the perplexing emblematic figure Wedekind introduces from some other dimension, but I think much of this effect is subsumed by the music, which comes from a future dimension of its own.

Kevin Adams' lighting intensifies the leap from 1891 to 2007 with its unusual, striking use of neon. The performers, as I've said, are inseparable from the material. Gallagher's Moritz is sometimes unnecessarily extreme in his neuroses, but that fits the charismatic intensity of the rock parallels. Groff and Michele are gorgeous, and she is heartbreaking in her innocence.

Surrounded by 15 young people, Christine Estabrook and Stephen Spinella have the juicy task of playing all the adults, one more awful than the other. They still hint at the ignorance that fuels adult cruelty, especially in Estabrook's portrait of Melchior's mother, whose failure is more terrible as she seems so understanding.

Bleachers on the sides of the stage accommodate both cast members and audience, as if to insert us into the play and vice versa. It's no gimmick: "Spring Awakening" spills off the stage into the emotional life of us all.

At the Eugene O'Neill Theatre; call 1-800-432-7250.