The drama of the gifted young adult Avril Lavigne’s authentic Under My Skin BY CARLY CARIOLI

The waltz, H.L. Mencken once wrote, never quite goes out of style. "It does its work, not like a college-yell or an explosion in a munitions plant, but like the rustle of the trees, the murmur of the illimitable sea, the sweet gurgle of a pretty girl." Mencken’s description of the waltz — "sneaking, insidious, disarming, lovely" — came to mind one day when my four-year-old daughter, Kaia, was dancing around our living room, as she often does, to Avril Lavigne’s Let Go (Arista). Although not actually waltzes, Avril’s "Unwanted" and "I’m with You" are close enough. (On her My World DVD, two of her bandmates are caught trying to learn the waltz in their dressing room.) Av’s girlish, fly-away melodies float off their modern-rock hinges in a similar three-quarter time, not with full-speed-ahead propulsion but with a sad, hesitant, uncertain elegance.

As my daughter’s sweeping, twirling steps met the songs’ swooning accents along an intuitive, loping gait, I thought about how Avril’s tunes are the perfect soundtrack for young girls lost in their own private, twirling reveries. In 1995, Alanis Morissette’s "You Oughta Know" codified angry young-womanhood in the voice of an avenging angel. Seven years later, Avril’s "Complicated" marked a seismic shift in tone for girls young enough to be Alanis’s little sisters. Av’s first line in that song could’ve been interpreted as a gentle rebuke of her snarling elders: "Chill out, whatcha yellin’ for?/Lay back, it’s all been done before."

Let Go focused not on externalized rage but on internal dialogue: its songs evinced the quiet yearnings of a girl who (most explicitly on "Things I’ll Never Say") feels incapable of making herself heard. Here’s a description of so-called "gifted" children — a designation that gained credence in the ’70s, just before Avril was born — from Linda Kreger Silverman, a PhD at the Gifted Development Center in Colorado: "Idealism, self-doubt, perceptiveness, excruciating sensitivity, moral imperatives, desperate needs for understanding, acceptance, love — all impinge simultaneously. . . . Their vast emotional range makes them appear contradictory: mature and immature, arrogant and compassionate, aggressive and timid. Semblances of composure and self-assurance often mask deep feelings of insecurity."

Which is pretty much Let Go in a nutshell. Here was a 16-year-old struggling to define herself out of a tangled web of contradictions. What struck some as outright hypocrisy — a professionally groomed, painstakingly produced singer marketed as a rock-and-roll alternative to pre-fab teen pop — impressed me as a worthy metaphor for the challenge of young-adulthood. The truth of Avril is in those contradictions, in all the details she hasn’t quite worked out yet. The boy in "Complicated," the one who’s a sweetheart in private and a preening slug around his pals, isn’t immature or fake but entirely typical. In the song, he and Avril are enacting an old dance — a waltz, if you will — and their teetering, halting steps toward each other are part ritual, part negotiation. Artifice — dressing up, role playing, striking poses — is the stuff that childhood is made of. It isn’t until those teenage hormones kick in that authenticity becomes an issue. And even then, authenticity is entirely provisional — you try to figure out which mask fits best. Or, as "Complicated" puts it so perfectly, you take what you get and turn it into honesty.

LET GO’S BIGGEST HIT, "Sk8er Boi," was a ringer — both in style (its full-bodied punk-pop roar) and in theme (romantic vindication). But it became an emblem for the album’s appeal. It’s the kind of updated fairy tale the Disney Channel puts on in the afternoon — a twist on West Side Story–style doomed romance, with a don’t-judge-a-book-by-its-cover message dressed up in skateboards and MTV stardom. The popular girl loses out; the tomboyish underdog gets her man and they ride off together into the bright lights of an arena tour. (Its narrative arc is so distinctly Hollywood that it’s being adapted into a major motion picture.) But on Under My Skin (RCA, in stores this Tuesday), whatever faith Avril had in fairy tales has been dispersed. Skin’s second single, due to hit the air next month, could almost be the opening scene from a "Sk8er Boi: The Movie" sequel. "You were everything that I wanted/We were meant to be, supposed to be but we lost it," she sings, before summing up the aftermath: "So much for my happy ending." None of her kid-sister-rock peers — a class that now includes Michelle Branch, Kelly Osbourne, Lillix, Hilary Duff, Katy Rose, Fefe Dobson, Skye Sweetman, and Toby Lightman — has hit the post-adolescent sweet spot of petulance, boredom, and loneliness quite so squarely.

Under My Skin is a more directly confrontational album in both sound and substance. Avril may have unplugged herself from the Matrix, but she’s found the freedom to act her rage. When addressing the thorny issue of sex on Let Go, she put off her suitor with an elaborately light-fingered tactical delay. "I know I’m not ready," she sang, but "tomorrow it may change." On Under My Skin’s lead single, "Don’t Tell Me," she finds herself in the same situation and goes for the jugular. Her boy’s attempt to get into her pants brings a torrent of threats — "I’ll have to kick your ass" — and a more general tantrum: "Don’t try to tell me what to do, don’t try to tell me what to say."