311, UNWRITTEN LAW, PAPA ROACH, USANA Amphitheatre, Saturday.

WEST VALLEY CITY — Reggae-rock band 311 knows how to throw a birthday party.

The lights, sounds and energy of dual vocalists Nick Hexum, S.A. Martinez, drummer Chad Sexton, guitarist Tim Mahoney and bassist P-Nut (born Aaron Willis) — known to their fans as 311 — got the 6,600 concertgoers at the USANA Amphitheatre out of their seats and dancing. It was a celebration, as this year marks the band's 15th anniversary.

Along with the music and lights, the band highlighted its set with some background images that flashed on a digital checkerboard screen behind Sexton's drums.

"Omaha Stylee," "Freak Out" and "Misdirected Hostility" were first out of the gate. "Beautiful Disaster" and a new song, the title track to the band's new album "Don't Tread on Me," shot streams of adrenaline through fans' systems.

Hexum and Martinez paired off with verse and chorus and got the audience singing along throughout the event. And not to be overshadowed, both Mahoney and P-Nut kept the music's dynamics intact. And emotional jams of "Silver," "Summer of Love," and "Freeze Time" rocked the audience.

Down near the stage, the general admission crowd slammed and moshed about while those sitting in seats had a hard time staying in them.

Even fans on the grassy area in back had their own little mosh pit going as those around them made way for flaying arms and bobbing heads.

Vintage 311 grooves, such as "All Mixed Up," "Come Original" and "Creatures for a While," shuffled it up with more new songs, "Frolic Room," and "It's Getting OK Now," which made its live-performance debut at Saturday's show.

One of the highlights was the drum-quartet segment during Sexton's solo on "Applied Science." After the initial syncopated pounding, roadies provided the other four band members some tom-toms and cymbals for a 311 drumline performance. Drum rounds and play-offs had the audience slamming and cheering for more.

The band let the crowd mellow out with the dreamy "Amber" and got the chanting going with "Beyond the Gray Sky."

The group's breakthrough single "Down" was nice rocking surprise, as was "Feels So Good." The two-song encore featured "Flowing and "Do You Right."

Opening the night was the punk bob of Unwritten Law and the explosive metal groove of Papa Roach.

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