PHILADELPHIA — Pharrell Williams, half of the hip-hop production team the Neptunes and member of the funk-rock band N.E.R.D., took a moment to explain his musical philosophy to the crowd at the N.E.R.D. show Saturday night.

"I dig all kinds of beats and I'll do the f--- what I want to do," he said, while the crowd of approximately 900 at the Trocadero roared in approval.

With baggy jeans, T-shirt, baseball hat and arms full of tattoos, Williams looked more like a skate punk than a hip-hop production don. Musically, N.E.R.D. (an acronym for "no one ever really dies'') energetically spanned the genres of rock, funk, R&B, hip-hop, folk and soul.

However, one didn't need a pocket calculator to determine that one member of N.E.R.D. was missing: Chad Hugo, also the other half of the Neptunes, was not present and is not a part of the 12-city tour.

"He's a family man,'' said Christian Twigg, bassist for Spymob, N.E.R.D.'s backing band.

While N.E.R.D.'s rapper Shay (that's Sheldon Haley, Williams' and Hugo's high-school pal from Virginia Beach) made the show, Williams was firmly the center of attention. Despite not having the strongest of singing voices, Williams is a charismatic stage presence who conveyed a sense of fun while telling ribald anecdotes and leading the audience in various chants.

What happens when you come home and "your bad ass babe is kissing another girl?'' Williams asked. The answer was provided in "Tape You,'' from N.E.R.D.'s album In Search Of ...

The audience was pogoing, participating in a call-and-response and moshing at various times.

Spymob aptly backed all of N.E.R.D.'s musical excursions, pounding a funky rhythmic base on "Stay Together,'' providing a soulful folkie shading on "Bobby James'' and finally rocking the house on the band's hit "Rock Star.''

"They had a lot of pure energy," Matt Krykew, 17, of West Chester, Pennsylvania, said. "I come to a lot of hardcore shows here and it was just about the same.''

The show was performed revue-style with statuesque singer Kelis, who came to help Williams perform the song "Truth or Dare.'' Then, Kelis, a member of the Neptunes' Star Trak Entertainment group, had a solo turn, singing the keyboard-driven R&B number "Popular Thug'' and the bouncy "Junkie.'' Later, rapper Lee Harvey came out to help the guys sing "Lapdance.''

N.E.R.D. also performed a new track, an uptempo song that seemed to recall a lighter 1960s Motown style.

Williams, who didn't identify the song, thought it sounded more like something from another era.

"You will bounce and dance like 'Wake Me Up Before You Go-Go,' " Williams told the audience, referring to the bubbly 1984 Wham! hit.

For the encore, Williams performed snippets of Busta Rhymes' "Pass the Courvoisier, Part II'' and Jay-Z's "I Just Wanna Love U (Give It 2 Me),'' both of which were produced by the Neptunes, while wrapping things up with N.E.R.D.'s "Run to the Sun'' and "Stay Together.''

Minneapolis' Spymob, who also played on N.E.R.D.'s In Search Of ... album, performed a 40-minute set before supporting the headlining act. Contrary to the hard funk-rock beats garnering much of the attention for N.E.R.D., the four-member Spymob employed a smoother, harmony-enhanced blue-eyed soul sound fortified with a rock and roll foundation. "2040'' featured a spacey guitar riff and a soulful groove, while "German Test Driver" was pepped up by a speedy Euro-pop beat. Fun yet mature, Spymob, who were signed to Epic in the late '90s but never released an album, are currently recording an LP for the Neptunes' Star Trak imprint.

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