Lolla-gal-ooza! : Main Stage: Women lead the way, with Courtney Love focusing on artistry, not antics.

Lollapalooza organizers keep telling us that the ambitious concept behind the annual, one-day summer camp for alternative-rock fans is more important than any single act on the bill.

Wrong.

When you think of past Lollapaloozas, it’s not the art exhibitions, the specialty food booths or even the smorgasbord of bands on two or more stages that mattered most.

Invariably, the defining moments are the one or two times each tour when specific bands step forward with the imagination and authority of the most liberating rock ‘n’ roll: Nine Inch Nails’s raw intensity in 1991, or Rage Against the Machine’s political urgency in 1993.

In its five years, no act has dominated a single day’s proceedings as much as Courtney Love and her band Hole did during Monday’s eight-hour marathon at the sold-out Irvine Meadows Amphitheatre.

And it was Love’s artistry, not her occasional sideshow antics, that mesmerized the more than 15,000 fans.

As usual, the flamboyant singer-guitarist defiantly planted her left foot on one of the monitors as she began singing her tales of anger and disillusionment, but she didn’t resort to the willful confrontation that has become a trademark of her performances.

While still generating sparks on such blistering numbers as “Violet,” she seemed to trust the more graceful and tender elements in her music, including a surprise version of “Pennyroyal Tea,” a Nirvana song she wrote with her late husband, Kurt Cobain.

The only time Love’s famous temper flared was when a fan sprayed her with water. After threatening to punch the fan--because the water could electrocute her--Love used the moment to comment on her self-destructive image.

“When I do die, it won’t be in front of you,” she told the audience. “I’ll die in a nice, quiet bed . . . with a tube [down] my throat.”

Most of Monday’s main stage lineup, however, was rather toothless. Only the zesty Elastica (filling in for the pregnant Sinead O’Connor) and the supercharged Sonic Youth (closing the show before a half-empty house around 11:15 p.m.) added measurably to the musical spirit on a day when the start was delayed an hour because of military flights in the area.

As we’ve seen in past tours, some acts that can be engrossing before a few hundred people in a club are simply stripped of their effectiveness when playing before several thousand in the daylight.

But it’s hard to imagine the Mighty Mighty Bosstones’ retro ska-punk approach being particularly interesting anywhere. Jesus Lizard’s David Yow had trouble projecting beyond the first 10 rows, and the freewheeling Beck seemed out of place in such a regimented format. Pavement is a quality band, but its approach is so low-fi and low-key that most of the audience took a dinner break.

Cypress Hill generated the wildest response of the day with its energetic brand of pro-marijuana, party-time rap, but it’s such a conventional, mainstream outfit (by contemporary standards) that you wonder why it is even on a tour that is supposed to be spotlighting challenging alternative music. The group’s B-Real is a charismatic leader, but how liberating can you be if your main message is simply to light up?

You could see the difference in emotional involvement once Hole took the stage. Where the fans danced to Cypress Hill, they seemed transfixed by Love’s gripping vision. On this day, she and her increasingly disciplined and exciting band were indeed virtually the whole story.