The more things change, the more Lemmy stays the same. He is a pillar of stability in the wobbly world of metal, where bands and trends come and go. Almost every Mot?rhead album sounds like the last, albeit with a couple new twists thrown in. And that's not a bad thing. Indeed, this 2004 platter serves up the expected blend of thrashers, midtempo grinders, and amped-up, old-time rock & roll, but Inferno feels like the group's spark has been rekindled. The most obvious infusion of energy comes from guest guitarist Steve Vai, who whips out his signature shredding technique on the thundering, rapid-fire "Terminal Show" and the sludgy "Down on Me." To Vai's credit, the legendary axeman adapts to Mot?rhead's style instead of showboating. Other surprises surface -- the melodic guitar leads of "Keys to the Kingdom" set over a bed of strings without bass or drums, and the acoustic blues ditty with harmonica ("Whorehouse Blues") that brings Inferno to a refreshingly low-key finish. The longest running line-up in Mot?rhead's history proves that old dogs may not always learn new tricks, but they can reinvent the old ones just fine.