Listening to Deja Voodoo , one has to wonder how long the members of Gov't Mule can keep producing music so inspired without overextending themselves. But that's like asking yourself how long a great instrumental solo can last, and this band's career has been tantamount to one long improvisation, from its earliest days as a trio comprised of guitarist/vocalist Warren Haynes, bassist Allen Woody (progenitors of the band while members of the Allman Brothers) and drummer Matt Abst (Dickey Betts' drummer in his Pattern Disruptive period), through the marathon Deep End project that ensued following Woody's untimely death.

If Mule music stayed fresh during that phase because of the perpetual rotation of musicians, the songs on the new album come alive because of the chemistry of what's now a permanent quartet. "Bad Man Walking" illustrates how the band functions: Haynes and new bass recruit Andy Hess (Black Crowes, John Scofield) are both adroit musicians who can rock, funk it up and improvise, while Abst and keyboardist Danny Louis are essentially journeymen who flourish here because they work here within strictly defined limits. Yet all four men obviously derive a great deal of pleasure playing together, as witnessed by the electricity of the studio improvisations that appear, even in abbreviated form, on cuts such as "Wine and Blood and "Perfect Shelter." The four-man Mule doesn't necessarily need an audience to generate excitement.

Deja Voodoo is potent, intelligent music, hard rock with brains. Songwriter Haynes pays as much attention to the lyrics on his tunes like "New World Blues" as producer Michael Barbiero devotes to the sequencing of tracks that give the near-two hour CD a tangible ebb and flow. There's almost equal amounts punch, thud and boom in the sound quality of songs like "About to Rage," but there's also deft use of space during the very same track. And while some of the material like "Mr. Man" is readily reminiscent of prior Mule—"Bad Little Doggie" in this case—the similarity is more a question of style than lack of new ideas.

Gov't Mule has never been shy about revealing its influences, which is why its live shows include such a broad range of cover material (from Johnny Cash to Zeppelin to Creedence). Yet the band transcends the derivative on "Lola Leave Your Light On," bringing a musicianly fervor to the performance of the primal riff-tune. Likewise, "My Separate Reality" is almost, but not quite, blues and the bass/electric piano/organ interplay redeems the Beatlesque "Silent Scream."

None of this material had been played live before The Mule went into the studio to record it. "Little Toy Brain," as unassuming a song as it seems, may turn out to be one of Deja Voodoo 's best vehicles for the stage, while the muted likes of "No Celebration" demonstrates just how soulful a singer Warren Haynes has become. And that's not to mention the artful intensity he brings to his guitar solos throughout the album, a focused, fiery approach that sets the pace for the whole band.