When the big beat boom gradually subsided, the Chemical Brothers initially sought refuge within a carefully crafted version of house music both epic and psychedelic.

Still, the duo are fusion fans at heart, and their fifth studio album, Push the Button, finds them easing back to their true love -- pulverizing stylistic boundaries while they seek out clever hooks to hang their production caps on.

The first half of the record is heavy on collaboration, beginning with the clear highlight, "Galvanize," which features guest Q-Tip riding a delicious mid-tempo groove and the brothers teasing out an ingenious Middle Eastern string sample over the course of several breakdowns and over six minutes.

"The Boxer" has ChemBros veteran Tim Burgess of the Charlatans UK coming on like an extroverted Steve Miller, while the next track, "Believe," features Britpop newcomer Kele Okereke (of Bloc Party) agonizing over an energized electroshock production composed of equal parts Prince and Chicago acid house.

It's clear the Chemical Brothers are still searching restlessly for new sounds and new fusions; only they could alternate a polemical hip-hop track -- "Left Right," a guest spot for Anwar Superstar, who, incidentally, may be the younger brother of Mos Def, but sounds like he's been living in Jay-Z's head for a few years -- with a feature for an indie band, the Magic Numbers ("Close Your Eyes").

Obviously, it's far more refreshing to explore new territory rather than merely go back over old ground; while "Come Inside" suffers by aping their 1997 approach, the subsequent track, "The Big Jump," finds the pair energized with a fresh gloss on their patented sound (although it is easy to notice how the skronky guitars in the background are clearly a post-electroclash development).

While there aren't as many heart-stopping productions as on 2002's unjustly neglected Come With Us, Push the Button proves the Chemical Brothers have retained the innate curiosity necessary to keep them blazing trails for years to come.