The Roots, guest Mos Def, play packed picnic

Philadelphia's Roots, led by drummer Ahmir "?uestlove" Thompson and rapper Tariq "Black Thought" Trotter, have been making music that combines catholic taste and rigorous execution for more than two decades.

And thanks to their presence as the house band on Late Night With Jimmy Fallon and ?uestlove's two-million-strong Twitter feed, the greatest live hip-hop band in the land has grown in status as pop cultural players.

That impact made itself plain this weekend at the fifth annual Roots Picnic, held at Festival Pier, which this year grew into a two-day affair. The two-stage picnic afforded the band the opportunity to put into play the full range of its interests, and the shuffle-culture festival did just that on Saturday.

The Roots closing set kicked off as a tribute to Adam "MCA" Yauch of the Beastie Boys, who died last month, with the Beasties' "Paul Revere," which the band played a second time when Black Thought realized his mic was dead.

By the time they left the stage three hours later, the Roots had brought up Washington rapper Wale (pronounced wah-LAY), who had sound problems of his own. And they backed up "daisy age" rappers De La Soul, who reached back to the 1980s in a loose, good-natured set that attracted old-school fans, giving this year's picnic an intergenerational and interracial familial vibe.

Also included was surprise guest Mos Def (the quick-tongued rapper also known by new name Yasiin Bey), who thrillingly went mic-to-mic with Black Thought on "Double Trouble" and "The Next Movement." As Roots performances go, though, this one wasn't as majestic or smooth as usual, with so many featured acts making for an unfocused evening.

But the day as a whole was a success. Afternoon performances by buzzed-about acts Shabazz Palaces and Danny Brown preceded DJ sets by Chicago electro duo Flosstradamus and LCD Soundsystem auteur James Murphy, who mixed disco-ball dynamics with post-punk and classic rock in a casually masterful turn at the turntables.

The table setters included Tune-Yards, the band fronted by the magnetic war-paint-wearing front woman Merrill Garbus. Looped drum beats and guitar licks were overlaid with live keyboards, saxophones, and bass, put over most effectively on the rebellious closer, "My Country."

As hot as Garbus' richly rhythmic music ran, the arty guitar rock of St. Vincent, fronted by frizzy-haired ax woman Annie Clark, was equally cool. She played dazzling guitar on "Cruel," added spooky theremin to "Northern Lights," and played a jagged cover of the Pop Group's "She Is Beyond Good and Evil," turning it into an indie-culture anthem with the battle cry: "Our only defense is together as an army."

The picnic was set to return Sunday, with Kid Cudi, Diplo, and Major Lazer, and with the Roots backing rapper Rakim.