The Liberation of Pearl Jam : Lead singer Eddie Vedder showed a disarming touch of humor and great rock ‘n’ roll instincts in the opening concert of the group’s U.S. tour.

SAN FRANCISCO â€”  Maybe it was all the cries of “Ed-dee . . . Ed-deeâ€� from the audience--rather than “Pearl Jam . . . Pearl Jamâ€�--that gave Eddie Vedder the idea as he waited backstage for the encore Thursday at the Warfield Theatre.

Maybe it was the record-breaking 950,000 copies his group’s new album sold last week--confirmation that Pearl Jam now rivals Guns N’ Roses as the hottest American rock band.

Maybe it was the way the media keep calling him--along with Nirvana’s Kurt Cobain--a spokesman for the ‘90s generation of alienated and angry youth.

Or maybe Vedder just wanted to have some fun amid all the pressures surrounding the opening date on the Seattle quintet’s much anticipated new U.S. tour.

Whatever it was, the charismatic singer showed both a disarming touch of humor and great rock ‘n’ roll instincts by tossing away the night’s planned set list and leading the band through an impromptu version of the Who’s “My Generation.�

By playing one of the most enduring anthems in rock history, Vedder made a wry jab at all the talk about him being a spokesman.

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At the same time, he sang and played guitar with such conviction and heart that he made it clear that he, like the old Who or the contemporary Bono, believes in the liberating power of music.

It has been easy to be suspicious of Pearl Jam, but it was moments such as that one Thursday that suggested there is far more reason to cheer the group’s extraordinary success than to fret over it.

Here’s a band that started in 1991 with such a reliance on tried and true rock sounds that it seemed as much pose as passion. You couldn’t have designed a more commercially potent band if you had sat down with your computer and a piece of magical software.

Most of Pearl Jam’s music on its hit debut album, “Ten,� was overly reminiscent of several ‘70s models--nothing as shamelessly derivative as the Black Crowes, but still echoing everything from the explosiveness of Led Zeppelin to the bluesy rhythm tension of the Allman Brothers. And Vedder rolled his eyes with such brooding anxiety as he prowled his way around the stage that you couldn’t help imagining him spending his summer vacations studying Jim Morrison videos.

At a time when several other acclaimed bands, notably Nirvana, were infusing rock with a new, punk-inspired daring, Pearl Jam seemed both conservative and a touch artificial.

But the test of a band rests in its work and Vedder showed increasing maturity over the last year--first by his stirring rendition of “Masters of War� at the Bob Dylan tribute concert in New York and then by his endearing set with the Doors at the Rock and Roll Hall of Fame dinner in Los Angeles.

In Pearl Jam’s new “Vs.� album, Vedder shows equal growth as a writer, just as the band--which also includes bassist Jeff Ament, guitarists Stone Gossard and Mike McCready and drummer Dave Abbruzzese--demonstrates far more character and range in framing Vedder’s lyrics.

Pearl Jam still doesn’t reflect the cutting-edge artistic vision of Nirvana, but there is a welcome, revolutionary element in the group’s music and stance.

Much the same as Metallica brought intelligence and commentary to the brutality of metal, Pearl Jam combats the macho posturing and indulgence of hard rock by focusing on sensitive and purposeful themes.

While Vedder touches on everything from racial injustice to the nation’s obsession with handguns, he is at his best on songs that express the loneliness and confusion of growing up, including physical and psychological abuse.

The band included seven songs from the new album in Thursday’s 90-minute set, which started off surprisingly sluggish.

Unless there was a power shortage at the 2,200-seat theater, the band made a mistake by performing the opening song in virtual darkness. The move may have been a sly commentary on all the fascination with Vedder--a reminder that this is a band and it’s the music that matters. It came across, however, as clumsy and self-conscious.

While the audience cheered mightily when the lights finally came on, the band seemed mechanical and stiff. Vedder, especially, seemed wary of any move that would draw attention to himself.

Instead of his nervous, convulsion-like shakes familiar on past Pearl Jam tours, Vedder stayed close to the microphone and put all his energy into his intense, sometimes screaming vocals.

Sensing the flatness, Vedder made another break from the planned set list about a half hour into the show, turning to “Rearviewmirror,� a terrific song from the new album that deals with the triumph of breaking away from personal chains.

One of the few times in the show that Vedder played guitar, he exhibited such determination and force that you could feel him literally pull the band--and the show--up to another, intoxicating level.

Virtually reflecting the song’s theme, the band members seemed to break through their own tensions growing out of the expectations surrounding them at this still early point in their career.

Pearl Jam’s ability to find more such moments of inspiration on the tour--which continues Tuesday and Wednesday at the San Diego Civic Theatre and Friday at the Empire Polo Club in Indio--should do much to tell us whether they can indeed live up to those lofty expectations.

Vedder, for one, appears ready for the challenge.