It’s hard work to stay at the top of a field as mercilessly mutating as dance music. And "Galvanize," the first track on the Chemical Brothers’ fifth full-length, suggests that, eight years after their mainstream breakthrough, Tom Rowlands and Ed Simons might finally be ready for the cutout bin.

"A Tribe Called Quest’s Q Tip’’ delivers a dull, witless rap over a relentlessly repetitive 6 1/2-minute big-beat groove that fails to get the party started.

So skip it. And don’t worry: They may not be innovating anymore, but the Brothers still know how to work it out. Because starting with "The Boxer," a stuttering groove with vocals by Tim Burgess of Charlatans U.K., and the thumping "Believe," with Kele Okereke of Bloc Party, Rowlands and Simons get back on track.

Stepping into the role usually reserved for Beth Orton, Anna-Lynne Williams does the ethereal female vocal turn on "Hold Tight London," which starts in the chill-out room, then makes its move to the dance floor.

The Brothers would do well to note that Button’s finest creation, the elegantly paced closer "Surface to Air," takes care of its trippy, ecstatic business without the distraction of a guest vocalist.

Grade: B

© 2005, The Philadelphia Inquirer. Distributed by Knight Ridder/Tribune Information Services.

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