Theoretically, aging wouldn't be that difficult of a trick for ZZ Top to pull off, since the little ol' band from Texas is thoroughly grounded in the blues, an ageless music that can sound equally good from the young and old alike.

After all, countless blues-based musicians, from Lightnin' Hopkins and Muddy Waters to B.B.

King and the Rolling Stones, have aged gracefully, albeit in varying degrees.

So why does ZZ Top sound so stiff and useless on XXX, a record celebrating their 30th anniversary? Part of it could be that the songwriting is decidedly weak, but a band as seasoned as ZZ Top should be able to make third-rate material at least listenable.

The real problem is that the band long ago sacrificed organic rhythms for a steady synthesized pulse.

They suggested this even before 1983's Eliminator, but that record was a bizarre, unpredictable masterstroke; after all, nobody would have predicted that a blend of Texas blues-rock and new wave drum machines would work, let alone flourish.

The problem was, the massive success of Eliminator made ZZ Top reluctant to abandon that sound.

That was OK for Afterburner, since it was released at the tail-end of the new wave era, but on every album since, they retained the steady click track, even as they stripped away the synthesizers.

Each album of the '90s suffered because of this, but somehow, XXX really reveals the extent of the damage, possibly because it should have been a celebratory release, possibly because it ends with four tracks that were recorded live but sound as processed as the eight studio cuts that precede them.

There is no grit, no sensuality to the music, no propulsion in the rhythm, and no joy to the playing.

Even when the band stretches out, they feel tightly wound, and there is no spark to Billy Gibbons' guitar playing.

If there was, maybe the three-chord shuffle of "Poke Chop Sandwich" would feel right, instead of a bastardized, emasculated knock-off of "Pearl Neckless." But there is nothing to the songs and nothing to the performances.

Ironically, ZZ Top doesn't follow the advice they offer in "Fearless Boogie": they're too scared of sounding organic to really let loose and boogie, or play the blues like the accomplished veterans they are.