Of course the reunited Police belonged at Bonnaroo, the festival built on jam bands. What disappeared when the band broke up in 1983 was a chance to hear the interaction of three musicians whose blend and friction forged one of rock's most original ensemble sounds. They left behind terse, neatly arranged studio albums and a few live recordings. Now, on tour again, they are jamming the alternatives. Their Bonnaroo set interspersed familiar arrangements with new ones, often within the same song. There were sparks, teases, intriguing excursions and a few misfires, but the Police sounded vital, still fascinated by Sting's songs and ready to tear into them anew.

It was the same set list, more or less, that they have been playing on their current arena tour, and the 100-minute set was 50 minutes shorter than the Bonnaroo schedule promised.

Sting's songs about loneliness, breakups and a growing social conscience have held up well. And as a band, the Police have their old strengths: Sting's springy bass lines and his reedy, fervent, undiminished voice; Stewart Copeland's drumming, with its mixture of thwacking propulsion and flurries of jazzy detail; Andy Summers' resourceful guitar parts creating all the harmony with watercolor transparency. They can charge into a song like 'Message in a Bottle' - with not just a fast beat but little flickering cymbal counterpoints - or disassemble and reassemble it, as they did with 'The Bed's Too Big Without You'. Some songs, like 'Every Little Thing She Does Is Magic', were rebuilt entirely; others, like 'Roxanne', metamorphosed in and out of the hit version.

Every so often, Mr. Summers stepped forward - as he never did on the Police's studio arrangements - for an extended, bluesy guitar solo, as he did to stoke 'Driven to Tears'. In 'When the World Is Running Down, You Make the Best of What's Still Around', Sting abandoned his recorded bass line to improvise high-speed, jazzy countermelodies while he and Mr. Summers stood shoulder to shoulder. Not every remake was an improvement; 'De Do Do Do, De Da Da Da' grew too relaxed. But 'Walking in Your Footsteps' worked multiple variations on its old self, and 'Walking on the Moon' plunged deeper into its reggae groove.

Like other reunited bands, the Police could easily have copied the versions of their songs that everyone remembers. But as musicians, they'd rather jam a little.

© The New York Times by Jon Pareles