System of a Down has been grouped into the current wave of prog-rock bands, and certainly this Los Angeles quartet possesses the adventurous musical chops to be compared favorably with such equally talented acts as the Mars Volta and Queens of the Stone Age.
At the same time, the band also defies such categorization by steering clear of the bloated self-indulgence that has been a hallmark of the genre since the '60s. Its excellent new album, ''Mezmerize," clocks in at an astonishingly compact 36 minutes -- or the average length of a Mars Volta song-suite.
None of which is to imply that System of a Down -- lead singer Serj Tankian, singer-guitarist Daron Malakian, bassist Shavo Odadjian, and drummer John Dolmayan -- doesn't remain the most wonderfully bombastic band in modern rock. Who else would have the nerve -- or the brains -- to shift between spot-on funky R&B and breakneck thrash on ''B.Y.O.B." (Bring Your Own Bombs), the album's first single? In between these battling beats, there's Tankian and Malakian's pulverizing vocals, punctuated by the jackhammer refrain, ''Why don't presidents fight the war / Why do they always send the poor? / Why do they always send the poor? / Why do they always send the poor?" It's as distinct and memorable a song as the extraordinary ''Chop Suey!" from the 2001 breakthrough ''Toxicity."
As with that album, the band remains politically minded, but never at the expense of a rockin' good time. With its jousting time signatures (a band staple), ''Revenga" is just as engrossing, and the album sustains its ferocious energy throughout. Certainly, there's so much going on during the run of a System of a Down song -- grinding metal gives way to a kind of tarantella, which then excuses itself for a disco breakbeat -- there's no room or time for boredom or distractions.
If bands such as the Pixies and Nirvana perfected the soft verse/hard chorus/soft verse song formula, System of a Down has cornered the market on schizophrenic musical dynamics morphing from one line to the next. Nothing about where these songs begin gives any indication as to where they will end up. ''Radio/Video" tempers its aggressive opening with downright lovely harmonies between Tankian and Malakian (who also handle all songwriting duties), before spinning off into a hoedown.
''Violent Pornography" begins with an almost cartoonish chant (albeit one with four-letter words) and rails against the brainwashing effects of television. ''Question!" launches with a battering ram of guitar and drums, which dive-bombs throughout what might otherwise be an acoustic ballad. All method and madness, it's a joy ride without limits.
''Mezmerize" is the first part of the planned two-disc set, which will conclude sometime later this year with ''Hypnotize," and one can only hope that disc is as solidly enjoyable as this one. Every song here has the boundless urgency and melodrama of a Broadway show tune -- but in a really good way. This isn't just rock 'n' roll, it's an exhilarating brand of goofy, glorious performance art.