PORTLAND, ORE. -- The voice of rage is shouting into the well of mellowness, and there is hardly an echo.

Zack de la Rocha, lead singer for the punk-thrash-rap group Rage Against the Machine, wants insurrection. He wants this alarmingly clean-cut group of Pacific Northwest teens and college students to vent their fury.

First he tries firing a salvo at militarism, but the crowd remains resolutely unincited. Then he ridicules complacent baby boomers: "Our parents' generation -- the do-nuthin' generation!" he rants to silence.

It's not that the crowd doesn't like the band -- Rage is actually one of the audience's favorites. Here at Lollapalooza, the "alternative" rock festival, a certain amount of righteous indignation is de rigueur. But as far as the crowd is concerned, that's the band's job.

De la Rocha desperately tries another target: Lollapalooza ticket prices (about $30 this year). He contends that these very fans before him are the dupes of money-grubbing promoters.

Finally, a lazy chorus arises from the crowd: "You're still getting your share, aren't you, buddy?"

Summer has come and so has Lollapalooza, rock-and-roll's biggest traveling road show, countercultural barometer and aural equivalent of staring into the sun. Now in its third season, the festival faces something of a dilemma. Because of its reputation as the leading showcase for "alternative" cutting-edge music, Lollapalooza promoters risk a measure of self-incrimination in owning up to the show's success. In previous seasons, the festival did booming business while the recession was taking the zing out of most summer concert offerings. With 37 dates booked across the country this year -- drawing crowds of up to 30,000 (although the Portland show last week topped out at 17,000) -- how alternative can a thing be?

The secret has gotten out. The term "alternative" was once a generic designation for music -- of whatever style -- played late at night on college radio, with album sales likely to be measured in the hundreds. But since such "alternative" bands as Lollapalooza sojourners Pearl Jam and the Red Hot Chili Peppers have gone platinum and Lollapalooza has ascended as one of rock's primary arbiters of taste, the vaporous concept of "alternative" has steadily gathered form.

Now, in 1993, it's a genre of music in its own right. And practically mainstream. An increasing number of radio stations designate their format as alternative, and the sound is pervading Top 40 stations as well.

"Alternative music is to the '90s what new wave was to the '80s," says Les Claypool, front man for festival headliner Primus, as he sips an amino acid-laced "smart drink" in the band's makeshift dressing room at Portland Meadows. "But don't say that!" he adds, waving off the suggestion. "I mean, nowadays people hear the term 'new wave' and they start gagging."

Call it progressive or postmodern or alternative, music fans have a pretty good idea of what they're likely to be getting under the Lollapalooza umbrella. That's best demonstrated by the fact that the festival's Chicago date sold out 30,000 tickets before the bands were even announced. (Lollapalooza reaches the D.C. environs July 20; this year it's being staged at a racetrack in Charles Town, W.Va., to give the 25,000 revelers more room.)

None of this, however, makes it particularly easy to sum up neatly just what alternative music has come to mean. This year's festival lineup is a good illustration. There is the agit-punk of Rage Against the Machine. For metalheads, Alice in Chains picks up where Black Sabbath left off. Tool sounds exactly like a visit to the Black & Decker section of the hardware store. All-black ensemble Fishbone plays hard rock. Belgian band Front 242 holds up the techno front. Arrested Development represents the "alternative rap" faction: hip-hop with a soulful, melodic and jazzy twist. Dinosaur Jr sonically resembles Neil Young on an extremely bad hair day. Babes in Toyland are a key band in the wave of aggressive she-rockers.

And then there is Primus, which Rage guitarist Tom Morello calls "the weirdest band on Earth," with Claypool's coyote twang crackling against the apocalyptic thunder of bass and rhythm lines. Add in the second-stage acts -- from Unrest to Mercury Rev to Tsunami -- and you've got a fuzzbox grab bag of music supplying the most decibels for your dollar.

If anything unifies these acts, it would be their disregard for commercial considerations. And this infuses their work with a vitality and honesty.

Alice in Chains bassist Mike Inez puts it this way: "You just have to be yourself and play the songs you want to play, the way you want to play them, and people accept that. We always try to tell the truth in our music."

This laissez-faire approach -- the ethic seems to be to let rock-and-roll find its own level -- carries over to other aspects of the tour. While musicians may fairly seethe with attitude onstage, they are surprisingly unassuming otherwise, and many can be seen throughout the day munching hot dogs and sharing beer with the fans. Most of them don't act like rock stars and don't seem to think of themselves as such. Sure, they hope the tour showers them with attention, but most say they're mainly interested in having a good time.

"The atmosphere here is very relaxed and mutually supportive," says Daniel B., Front 242's keyboardist and computer programmer. "In other festivals we've played, there tends to be a lot of stress and competition."

Indeed, there is a laid-back ambiance to the festival, at least at this stop (the tour's third date), that seems incongruous with the often harsh tone of the music. A good measure of Lollapalooza Zeitgeist is the "mosh pit," where everyone scrunches up close to the stage and slam-dances. The lucky ones find themselves flung up to body-surf atop the crowd, and the really lucky ones are hurled over the railing to plop down on the catwalk bordering the stage.

While moshing started as a gesture of anarchist rage, it too has gone mainstream. More than a dozen security guys guard the stage, but their mission has less to do with defending the musicians than accommodating the mostly teenage moshers, who are given a pat on the back and sent trundling into the wings, their faces lit up like they've just gotten off a thrill ride.

And for that matter, moshing seems to have become the mood-enhancer of choice for concertgoers. A visit to the first-aid tent confirms this. "A few bloody noses and black eyes," says a medic. "Moshing-related injuries. Some dehydration. Two kids drank too much beer."

"Scary, isn't it?" Ted Gardner, the show's main producer, says slyly. A burly Australian rock-and-roll survivor with earrings and buzzed gray hair, Gardner has taken over organizing duties from Lollapalooza founder Perry Farrell, former lead singer for the band Jane's Addiction. He's now touring with his new band, Porno for Pyros.

Gardner has to perform a delicate balancing act. For one thing, "it's important that we not have the reputation of being like kids' parents, but at the same time we have to act as responsible adults."

Then there's this "alternative" bugaboo. "There's a balance that has to be struck between commercial viability, and to use a very bad adjective, 'alternative' music," he says. He admits that the current lineup lacks the break-out successes of the past two festivals, which boasted such prominent acts as Ministry, Ice Cube and Pearl Jam -- although in some cases, success for these groups came in the interval between their signing up for the tour and actually doing it.

This year's tour was also heavily lobbied by record companies. Sony, for example, submitted tapes of 32 bands, and got four on the bill. While the festival would probably have no trouble attracting well-established groups, Gardner concedes that economics plays a role in the strategy. "We've got two objectives," he says. "To have great music and to make a buck. Some of the bands we talked to wanted too much money, and we don't want to have to raise ticket prices."

And, for that matter, why jack up the overhead when Lollapalooza itself has brand-name appeal? Many in the Portland audience were quick to voice the opinion that while this year's lineup wasn't a disappointment, it lacked the flash of last year's -- though that didn't seem to matter much. After all, from the beginning, the festival has shrewdly hedged its bets with the sideshows and spectacles of the Village, a tent community of vendors and performers.

"It's more fun just to people-watch," says Julie Palo, a fresh-faced 18-year-old Portland native. "Seeing the small bands on the second stage was way better than the bands on the main stage."

"The bill was better last year, but that was a hard one to top," says Jim Pirie, 24, a college student from Seattle. "But it's still interesting to hear the new music."

Meanwhile, '60s-style civil disobedience must at least be saluted, and the spot for that is a tent dubbed the Forum, where Timothy Leary could be heard, uh, "nattering," to use the word of Scott Bateman, who at 29 was one of the senior concertgoers. "Lotta nattering in there, mostly about logging."

"You're going to learn how to operate your eyeballs," LSD guru Leary declares against a background of electronic music. "You're going to learn how to reprogram your brain, how to turn chaos off and on. And then we're going to talk about Socrates!"

Hold that thought, Tim, while we go for a smart drink.