CHICAGO — As concepts go, the notion of pop acts going onstage to reprise their best-loved albums front to back isn’t particularly new. To conclude its 1989 “Green” tour, R.E.M. threw in a surprise set at its Atlanta homecoming show, playing its debut album “Murmur” in original track order as a no-fuss bonus for its fans.

These days, however, all quarters of the music industry are looking for ways to generate a marketable buzz as record sales plummet and recorded music becomes an ephemeral stream rather than some form of shiny disc. So the live restaging of a classic album, such as those that opened the Pitchfork Music Festival here on Friday, takes on more than novelty appeal. It’s not only nostalgia, but — since all the performances were based on original vinyl LP versions — an assertion of aesthetic endurance.

PitchforkMedia.com, the festival’s producer, may seem an unlikely booster for this rising trend, which gave rap supergroup Public Enemy occasion to reform around its 1988 album “It Takes a Nation of Millions to Hold Us Back,” along with Mission of Burma (“Vs.,” 1982) and Sebadoh (“Bubble and Scrape,” 1993). The leading Web site covering independent music is all about the hot download and the next big (yet modestly cultish) thing. But one of those things, along with nearly 40 other acts presented over the weekend, is this ritual nod to post-punk classicism.

Public Enemy’s two-plus-hour performance was as galvanizing as anyone could hope. Even though the group’s clowning, clock-festooned cartoon figure Flavor Flav was absent for the first two numbers, angering front man Chuck D., the sound was blazing. The rappers were backed not only by turntables but also by a full band that churned through hard, deep James Brown funk grooves and sticky, liquid polyrhythms — shot through with the group’s signature sound effects (piercing whistles, alarms, subharmonic bass blasts) — that evoked the swampy vortex of Miles Davis’s “On the Corner.”

This was mostly a backdrop for Chuck D. and Flavor Flav’s politically charged vaudeville, in which the former’s hard-edged commentaries (“Louder Than a Bomb”) alternate with the latter’s comical observations (“Cold Lamping with Flavor”). Rather than roll through their entire opus at a steady clip, the performers paused between tracks to extemporize with bits of history, rhetoric, and nonsense. At one point, when Flavor Flav, who has starred in his own reality cable show, went on too long about his new career, some in the previously enraptured (and 99% Caucasian) crowd began to boo. Flavor Flav angrily dismissed them. “You’re all fake-ass ghosts!” he shouted. Even if he couldn’t make the stage on time, the rapper is a sponge for attention.

Nothing else at the fourth annual Pitchfork fest, which drew an attendance of 45,000 people over three days at Chicago’s Union Park, matched Public Enemy for cultural impact. Unless one can include the presence of actress Julia Stiles, whose low-key attendance generated a lot of word-of-mouth chatter. “I’m off duty,” she told a Web logger who approached her for a comment during Spiritualized’s rousing Sunday evening set. “But I’ll read your blog.”

The range of bands, which included indie-rock heroes the Hold Steady, flavor-of-the-season buzz band Vampire Weekend, puckish English pop star Jarvis Crocker, rappers Ghostface Killah and Raekwon from the Wu-Tang Clan, and the singer-songwriter M. Ward, was catholic. But it also was generally less exciting than last year’s lineup, which boasted more experimental and rhythm-obsessed outfits such as Battles and Dan Deacon, in the midst of their next-big-thingdom. Instead, what listeners got was more predictable and reliable entertainment from bands stepping out of their usual late-night club environs into the bright sun and muggy air of the afternoon stage. Indeed, the bands that got the sometimes mud-spattered crowds energized tended to be blatant about their intentions: Brooklyn’s !!! (chik, chik, chik) conjured a huge dance party with its rubbery bass-and-drum patterns, and the multinational King Khan and the Shrines purloined R&B roadhouse revue shtick with a horn section, a dancer, and a costumed front man prone to extravagant outbursts.

Yet what continues to set Pitchfork apart from superficially similar events, such as Lollapalooza (staged next month at a different Chicago park) or Coachella, is its sense of intimacy (capacity is limited to 17,000) and inclusion of fellow travelers. There is an independent record market on the festival site, as well as a gathering of concert poster designers known as Flatstock. Food and beverage concessions are fairly cheap, and even the corporate sponsorship is of the “soft” variety, including Whole Foods and a local microbrewery.

“It’s got a community vibe and it’s down to earth,” Erin Frisby said. An employee of the Chicago nonprofit group Rock for Kids, she was monitoring a charity auction of items signed by various musicians at the festival — original mix CDs, posters, a ride cymbal from the Japanese metal band Boris (which fetched $500). For Ms. Frisby, 30, part of the appeal was the generational mix, of both performers and fans. “Everybody here is not 21,” she said. “People have so much more access to music because of the Internet that the old generational idea doesn’t exist anymore. It was just target marketing. Watching Public Enemy or Mission of Burma, you can hear a lot of their influence. It’s nice to see the history and the growth of the music.”

Pitchfork’s vision of a perma-rock utopia has sympathizers. One of the festival’s collaborators in its Don’t Look Back series, the British-based All Tomorrow’s Parties Festival, will stage its own event in upstate New York in September. The massively influential and long out-of-pocket band My Bloody Valentine will headline, and old-school college radio faves such as the Meat Puppets and Tortoise will perform vintage albums, along with many sets from the musicians who have followed in their wake.

“You know what it is?” Ken Shipley, a founder of the Chicago-based label Numero Group, asked, reflecting on the formula.

“It’s a Mexican restaurant. There’s three ingredients, but which way do you want it?”