Tastykakes. Hoagies. The Roots Picnic.

Philly likes its tasty traditions, and within four years of its start, hip hop's hometown heroes have turned their all-day concert at Festival Pier at Penn's Landing into a ritual of diverse musicality.

Before Saturday's sold-out show at the Pier, there was a "Pre-Picnic Appetizer" on Friday at the Legendary Dobbs with the Roots' MC, Black Thought, rapping with members of his ensemble's horn section to several of his band's classics, as well as a brassy cover of the O'Jays' "For the Love of Money."

The Roots Picnic started at noon Saturday with two stages holding the likes of Man Man and Ariel Pink. The concert became an event when the exquisite Esperanza Spalding performed, backed by the Roots. The Grammy winner for best new artist wasted no time schooling the crowd, stating "jazz isn't back; it never went away."

She proved her theory, jumping between stand-up acoustic and electric bass and allowing her high voice to sail wordlessly through a taut cover of Weather Report's "Predator."

The Roots served as a fusion jazz band as its keyboards grew aquatic and drummer ?uestlove paradiddled like mad.

With that fluid backing, Spalding sang a Latin-tinged version of her "I Know You Know" as well as a bubbling take on the Michael Jackson ballad "I Can't Help It."

That was not the last time Jackson was invoked. Nas - the night's co-headliner - powered through a version of "It Ain't Hard to Tell" that heavily sampled MJ's "Human Nature."

Earlier, chart-topping MC and marijuana enthusiast Wiz Khalifa, hit the ground running with a bass-squelching version of "Phone Numbers" with his double-tracked voice rubber-band elastic. His slippery delivery was even better on the electro-pop likes of "No Sleep" and "Roll Up."

Still, nothing was as celebratory as the Roots, who split their set with Nas. Black Thought and Nas are known for brooding cerebral raps and heavy flow. On Saturday, the two were in a lighter mood.

Thought, in particular, was having an uproarious time whether on the Roots' tense "How I Got Over," Kool & the Gang's brassy "Jungle Boogie," or James Brown's "The Boss."

The Roots were in full funk mode with tuba player Damon Bryson providing dense bass lines. What's not to celebrate? Nas took advantage of the Roots' backing with frenzied takes on several of his hits, including the raucous "Made You Look" and the psychedelic "Hip Hop is Dead." Then he passed the mike back to Thought for a speedy version of "The Seed (2.0)" and a sweet tribute to recently deceased vocalist Gil Scott-Heron - "The Bottle."