Smells Like Rock Classics : Nirvana’s Forum concert demonstrates why the Seattle group may be the most important American rock band since R.E.M.

Nirvana’s Kurt Cobain sang at times Thursday night at the Forum with an intensity so primal that he seemed fully capable of frightening physical acts.

Yet there were other times when his lyrics were so disarmingly vulnerable that he seemed utterly incapable of defending himself against even the slightest attack.

It’s Cobain’s ability to blend those conflicting emotions in his songs that made Nirvana’s “In Utero” the most compelling album of 1993--and establishes Nirvana as possibly the most important American rock group since R.E.M.

Wearing his trademark pajama top and jeans, Cobain led the Seattle-based band Thursday through a triumphant series of songs--from “Smells Like Teen Spirit” to “Heart-Shaped Box”--that are so immediately accessible, yet wonderfully mysterious, they already have the ring of rock classics.

Like Bob Dylan and Elvis Costello, Cobain favors lyrics that are deceptive--words that can not only mean different things to different people, but can also take on new meanings as one’s own attitudes and emotions change.

While he clearly writes from the position of an outcast, Cobain sometimes seems torn over the basic question of whether he wants to once again declare his independence or whether he yearns for the acceptance of all those who have pushed him aside over the years.

“I miss the comfort in being sad,” he says in “Frances Farmer Will Have Her Revenge on Seattle,” giving no clue in his delivery to whether he’s mocking his own isolation or finding solace in it.

Where there is a conscious, literary edge to much of Dylan and Costello’s work, Cobain writes in a more fragmented manner that makes him, in a strange way, the ideal poet for this dysfunctional age.

While seemingly built around arbitrary and conflicting ideas and images, the songs--with their appealing Beatlesesque melodic touches--abound with an alienation and anger that speaks to an unusually wide audience.

Without losing the punk-aligned fans that first embraced the band, the group now attracts everything from the collegiate hip to the mainstream curious to, encouragingly, a growing post-30 contingent that has discovered there is something in the band’s music that speaks to more than just the MTV crowd.

On a rare night when festival seating was utilized at the Forum, Nirvana--following opening sets by the veteran Butthole Surfers and the promising Chokebore--exhibited captivating force. Drummer Dave Grohl and bassist Krist Novoselic played with raw vigor and Pat Smear doubled on guitar with Cobain. Cellist Lori Goldston joined the group for acoustic versions of such songs as “Polly” and “All Apologies.”

Not everyone was pleased with the latter excursions. During one of the acoustic numbers, fans near the front of the stage heckled Cobain and threw two shoes at him. One shoe glanced off his head, while the other hit his guitar.

That’s the kind of crowd impatience that Nirvana should ignore, but there was another sign of frustration worth heeding. At the end of the encore, the group went through the old smash-the-guitar and drown-them-out-with-feedback routine that has long been part of its playbook.

Whether it was meant as a wry slap at rock ritual or a salute to the band’s own punk roots, the approach has become tedious. Rather than a bonus on the evening, dozens in the crowd took it as a signal to head home from the concert, a benefit for FAIR, an organization devoted to fighting media bias and censorship.

As Nirvana moves confidently into the new year, this is one part of its repertoire that is best left behind.