MANSFIELD - It was a good day for hip-hop.

Although the urban art form has been largely hijacked by values of materialism and fake thuggery, Saturday's Rock the Bells festival at the Comcast Center stripped away the debris to reveal rap's essence - clever rhymes, raw energy and real artists, not marketable façades.

There were no rappers endlessly plugging new albums or doubling as strippers, and MCs didn't need blinding chains and ill-fitting jeans to announce their presence, though they likely caught contact highs onstage from all the weed wafting in the air.

A number of fans missed opening acts and pillars of hip-hop such as Rakim and Dead Prez because of traffic bound for the country festival at Gillette Stadium. And while the order of the lineup could have been improved - such as placing West Coast phenomenon Pharcyde earlier in the set and pushing back East Coast mainstays Raekwon and Ghostface Killah - it was nevertheless an impressive group of some of hip-hop's premier artists.

Rae and Ghost delivered a typically set that included solo hits and Wu-Tang classics "Ice Cream," "C.R.E.A.M." and "Triumph," while also sending out one of the night's many shout-outs to late, great hip-hop producer J Dilla. Hip-hop fans that don't take their cues from the radio form a diverse set, but the artists on Saturday's bill were no less diverse, from the politically-charged Immortal Technique to the hippie-infused sounds of De La Soul.

The latter trio emerged sans blinding chains, dressed only in nondescript T-shirts and black pants. There was no mean-mugging, as the threesome was secure enough to be playful while rolling out old school joints and hits off their most recent album "The Grind Date."

Redman, who revealed he was operating with a hangover, delivered without scheduled sidekick Method Man, who was stuck in New York. The New Jersey MC kept the seats filled with help from one water-splashing hype man and a brief appearance from DJ Kool, who performed his 1996 smash "Let Me Clear My Throat."

The oddest set of the night went to Mos Def, who emerged covered in a blanket, singing. Though he appeared to be having fun while wailing over various beats, the crowd wasn't exactly in on the good times for the first 20 minutes of the set, when he seemed to confuse the rap festival with a tribal seance. Things picked up a bit about halfway through with an interlude of actual rap songs that included "Ms. Fat Booty."

As the night's final set after, A Tribe Called Quest managed to keep the energy high. Mos Def returned to play hype man and lyrical assistant for Q-Tip until his partner in rhyme Phife Dawg stepped onstage and the group lit into some of their classic hits including "Buggin' Out," "Oh My God," "Check the Rhime" and the ultimate posse joint, "Scenario."

Though not the night's final act, Nas was the best, quickly proving why he should be mentioned anytime a discussion of hip-hop's upper echelon takes place - with no gimmicks, hype men or corny side-to-side crowd chants, the Queensbridge MC delivered a perfectly paced hip-hop set that held the audience captivated from start to finish. As he ran through recent fare, a sizable chunk of his classic debut "Illmatic" and a number of mid-career hits, including "If I Ruled the World" and "One MIc," you got the feeling someone still cares about the state of hip-hop and the black community.

Earlier in the day, Redman posed a key question when he asked if the crowd remembered when rap wasn't about jewelry, cars and corny dances.

"Remember when hip-hop was good?" he said.

Saturday, they did.