They may be New Yorkers for five nights a week, but the Roots still know how to make their hometown feel loved. Saturday's Roots Picnic at Festival Pier was a sprawling, sweaty thank-you gift to the city they call Illadelph.

The Roots themselves opened the all-day affair with a short set before ceding the stage to a wide swath of friends and fellow travelers, including Public Enemy, TV on the Radio, Asher Roth, and Santigold, not to mention New Kids on the Block's Donnie Wahlberg and Jordan Knight, who stopped by on their way to a show in Camden. But whereas most summer festivals are curated with the coherence of an iPod on shuffle, the Picnic's performances augmented and informed one another, creating an expansive sense of community that enveloped the sold-out crowd.

The marquee event was Public Enemy's performance of their epochal 1988 album, It Takes a Nation of Millions to Hold Us Back, performed for only the third - and, they have said, the last - time on American soil, and the first time with a band.

Public Enemy's Chuck D famously called rap music African Americans' CNN, an analogy that bodes ill for the exhumation of a 20-year-old album. But fueled by an expanded Roots lineup that included a horn section from the Brooklyn-based Afrobeat orchestra Antibalas, Nation sounded like anything but old news. Chuck D's stentorian voice has lost none of its power to command, and Flavor Flav washed away years of reality-TV embarrassment, seeming more like a sharp-witted jester than a fool.

Rather than approximating Nation's sonic thicket, the Roots added melody and depth. The prison-riot saga "Black Steel in the Hour of Chaos" gained a funk guitar riff and blaring horns, with ?uestlove's snare hits ringing out like rifle shots.

It would be hard to imagine a more pronounced contrast with Public Enemy's activist urgency than the bratty, self-satisfied rap of Morrisville's Asher Roth, who followed. When the Picnic's lineup was announced, the message boards at Okayplayer filled up with complaints about Roth, but the younger fans who packed the side tent shouted along with his every word, eagerly following the advice of "Blunt Cruisin'."

A few of the Picnic's dishes went down less smoothly than others. Akron, Ohio, garage-rock duo the Black Keys played to a receptive but cooler crowd, still catching its breath after a calisthenic set by Philly-born dance-rapper Santigold. The Black Keys drowned out a highly anticipated side-stage set by Kanye West protege Kid Cudi, although if you stood by the tent's entrance you could imagine it was all part of a carefully orchestrated mash-up.

Although the crowd thinned after Public Enemy's performance, those who stuck around were rewarded with a blistering set by TV on the Radio, whose echoing noise rock also was augmented by Antibalas' horns, evidently trying to give the Roots a run for their money in the hardworking department.

By the time the Roots took the stage again, shortly before 11 p.m., exhilaration was giving way to exhaustion, but they hit the ground running, playing an hour-long set as if every song were the last one of the night. Dipping into their own catalogue and covers from heavy metal and blues rock, they summed up and distilled the day's vibrant and volatile mix, a bracing cocktail to wash down a splendid feast.