It was an action-packed ninth annual Roots Picnic at the Festival Pier on Saturday.

Shortly after the show kicked off at noon, Ahmir "Questlove" Thompson, drummer for the Philadelphia hip-hop and Tonight Show house band, made news by announcing that the Picnic will be adding a New York date this fall. On Facebook, he teased New Yorkers that the until-now Philly-only fest will be coming to "a park near you." (No specifics yet.)

About an hour later, another surprise: During a set by 15-year-old singer and fashionista Willow Smith, her rapper-actor father, Will, came onstage and performed "Summertime," a signature of his DJ Jazzy Jeff and the Fresh Prince days. It's said that summer in Philadelphia begins with the Roots Picnic, and the Smiths made it official.

Then, later in the show, a less pleasant surprise.

Maybe more than any other artist on the bill, the buzz act at this year's Picnic was Future, the Atlanta trap-rap star who also has a sold-out date with Drake coming up at the Wells Fargo Center on Aug. 21. He's hugely popular with young hip-hop fans, both black and white.

Future was scheduled to be the last act before the double-headlining duo of the Roots and Future's fellow Atlantan pop-R&B star Usher. He did come on, setting the crowd into a paroxysm of hip-grinding joy with his guttural voice and bottom-heavy beats.

But after 20 minutes of a scheduled hour show, the performance came to an abrupt stop. Two minutes later, Future came back, only to have the music halt again after a few moments, and the rapper left the stage, never to return. After 20 minutes of waiting and booing, the crowd moved on without getting an explanation.

Possibly to quell the crowd, the Roots hit the stage a few minutes before their appointed 9 p.m. start.

Dressed in jackets and ties for their only scheduled Philadelphia performance this summer - they are not on the Wawa Welcome America! bill on July Fourth for the first time since 2008 - the virtuosic ensemble started by busting out a 10-minute hip-hop, jazz-funk medley, with rapper Black Thought's rapid-fire, fiercely enunciated takes on tunes with "Don't Say Nothin'" and "The Next Movement" flowing effortlessly into one another.

Usher then joined the band, bringing megahits like the opening erotic rush of "Caught Up" with him. And of course, because this was the Roots, it came off as by no means a quickly thrown together mash-up, but instead a well-rehearsed and intelligently thought-out collaboration, with fresh Black Thought verses as a bonus. The band added musicianly swagger and serious bottom to the singer's often-too-slick tunes.

"There's something about that Philly bounce," Usher said before "U Remind Me." "It's a pocket like none other."

And he in turn brought a suave sexy confidence to bear on the Roots song he contributed to, singing the Jill Scott-penned hook, for instance, to their signature "You Got Me."

Earlier in the evening, the event had mellowed down easy with a pair of artists that took divergent rhythm and blues routes.

Dev Hynes, the British song stylist who used to be known as Lightspeed Champion and now records as Blood Orange, led a suavely modern ensemble on the north stage. Shirtlessly firing up a brand of indie bedroom soul replete with sax breaks and sleek lead guitar, Hynes offered a sampling from his upcoming Freetown Sound, his third under the Blood Orange moniker.

He was followed on the main stage by Leon Bridges, the retro soulman from Fort Worth, Texas, with a vintage sound and aesthetic that has led him to be likened to Sam Cooke. If Bridges doesn't have the vocal range to match the greats, his music has an easy going élan and old-fashioned charm that went down smooth on a sticky almost-summer evening before a crowd eagerly awaiting Future.

The Picnic, which lately has been short on the kind of indie rock acts like the War On Drugs and St. Vincent that used to be regulars, drew a racially mixed crowd of mostly millennial hip-hop and R&B fans, many wearing Muhammad Ali (or Cassius Clay) shirts to honor the late prize fighter.

The concert kicked off with British soul singer Jodie Abacus - the first of 24 scheduled acts.

By midafternoon, it hit a high point that was hard for subsequent acts to top with Anderson .Paak, the California rapper-singer-drummer who was making his Philadelphia debut with his band the Free Nationals.

For Philly hip-hop watchers, rising emcee Lil Uzi Vertcq pulled in an enthusiastic crowd on the small-scale Mosaic stage, with a sizable crowd spitting his street rhymes along with him. Janelle Monae protégé Jidenna - he of the polyrhythmic 2015 R&B hit "Classic Man" - put on a winningly energetic set.

Oakland singer and America's Got Talent veteran Kehlani moved a main-stage crowd with a mixture of hip-hop R&B that lashed out against untrustworthy men and soft-focus piano balladry.

Crowded and mostly held on blacktop on a largely shadeless pier, the Roots Picnic has often seemed misnamed, as the locale is not an inviting place for a picnic. Improvements have been made over the years, however, with much of the site now covered in sand and food options from local vendors more plentiful.

The difference this year, though, was that the site on Columbus Boulevard along the Delaware River had been expanded. The second largest of the three stages was not only situated a full city block north of the main one, it also included a large tented area that let concertgoers sit and chill and, if they so desired, watch main stage acts on a video screen.

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