Since the release of their 2006 self-titled debut, Aussie hard-rockers Wolfmother [ tickets ]'s major calling card has been singer/guitarist Andrew Stockdale's classic rock riffing, his enormous 'fro, and his banshee-like wail, which makes him sound like the mutant offspring of Robert Plant and Ozzy Osbourne. All appear to be intact on "Cosmic Egg," Wolfmother's second full-length album and first effort as a quartet.

After the original trio wrapped up touring in support of the their buzz-about debut, Stockdale split with bassist/keyboardist Chris Ross and drummer Myles Heskett. Yet he opted to continue to carry the Wolfmother banner after he hired a trio of new bandmates and hunkered down in the studio to record a followup. Not knowing the circumstances of the split, one can't fault Stockdale for carrying on with his vision. Despite Ross and Heskett's efforts, you'd be hard pressed to argue that they're as essential to Wolfmother as, say, Meg White is to The White Stripes. But one thing is clear: on its second album: the band has traded in its rough-and-tumble charm for arena-rock polish.

Depending on your perspective, that's not necessarily a bad thing. Wolfmother always had big-rock aspirations, albeit delivered through a scrappy power trio. Now as a foursome, with noted knob-twirler Alan Moulder at the helm, Wolfmother rocks with the bombast of their heavy-metal heroes Led Zeppelin and Black Sabbath, but unfortunately they don't sound quite as fresh as either, since their forefathers were laying down that monster riffage more than three decades ago.

That's not to say "Cosmic Egg" isn't worth digging into. Opener "California Queen" cooks like an unholy mash-up of Deep Purple's "Highway Star" and Black Sabbath's "Iron Man," but of course can't hold a candle to the originals. On "White Feather," Stockdale and company get the Led out, with Bonzo-like beats, Plant-styled phrasing, and tasty Page-esque riffs. "Fair Away" also seems inspired by Zeppelin, only its acoustic period, before morphing into a full-on power ballad.

Ultimately, "Cosmic Egg" isn't a bad listen, but if you don't have the albums by Stockdale's influences, it might be better to invest in those first. "Cosmic Egg" is not quite "The Song Remains the Same"; more like "The Songs Seem Vaguely Familiar."