{$The Mars Volta} are continual contenders for the mantle of most experimental high-profile {\metal} group, along with {$System of a Down}, an artist they've toured with but who usually sell 20 times more records. {$Mars Volta} aren't as popular, not because their riffs are less memorable or innovative but because their cycle of musical buildup and release, although similarly jarring, can last at least 20 minutes instead of {$System}'s two. (It's the difference between having a background in {\acid rock} and having one in {\thrash}.) While the early reports on third album {^Amputechture} commented that the duo of {$Cedric Bixler-Zavala} and {$Omar Rodriguez-Lopez} had learned a few lessons about silence and forsaken the concept album, don't believe it. The album is little different than their two previous atom bombs, {^De-Loused in the Comatorium} and {^Frances the Mute} -- tense and anxious, continually pushing the boundaries of extreme production, with long periods of dynamics that rise ever higher, followed by an explosion of release (usually screaming {\hard rock} with storms of atonal brass and horns). The album opens with {&"Vicarious Atonement,"} five minutes of spectral effects and piercing guitar that gets a boost at the beginning of the next track, {&"Tetragrammaton,"} and then blooms into full riffing glory after a few more minutes (and they're still nowhere near the end of the 16-minute track). {$John Frusciante}, eccentric genius from {$the Red Hot Chili Peppers}, returns on guitar, but {$Bixler-Zavala} and {$Rodriguez-Lopez} exert so much control over the sound of {$Mars Volta} that {$Frusciante} makes virtually no individual impression on this record, although most of the guitar work is his. (Granted, his presence leaves {$Rodriguez-Lopez} open for more intricate work on production.) {$The Mars Volta} are one of the most intriguing bands in {\rock}, but their huge musical power is often deflected by {$Bixler-Zavala}'s conceptual themes (which are difficult to follow, but also, perversely, impossible to ignore) and blitzkrieg dynamics that are either dialed down to one or up to ten (but rarely in-between). ~ John Bush, All Music Guide