Back in 1999, ZZ Top celebrated their 30th anniversary by releasing their 13th album, XXX. It's a wrongly overlooked, dirty little comet of an album that features both new studio and live recordings.

From the fuzzed-out cyborg rock of the opening "Poke Chop Sandwich" to the dark, appropriately cinematic blues of "Made Into a Movie" and on through the whacked-out sample- and organ-infused instrumental closer "Dreadmonboogaloo," the studio section of XXX covers a lot of territory in a big hurry. It's almost as if they forgot they had only 30 minutes to work with, and accidentally crammed in a normal album-sized helping of riffs and ideas.

We asked guitarist Billy Gibbons if it was true XXX was originally intended to be a full live album of new material. "The ZZ Top design at the time of release of XXX aimed at capturing what we enjoy out on the road," he explains. "And that's what we still enjoy …playing live and loud! The return to the studio in fact brought us into focus of the importance of playing in good tuning and good timing. And the result was a bit of both -- tracking in the studio and then bringing the material onto the stage."

Slightly altering the ratio of their legendary half-live / half-studio 1975 album Fandango!, XXX ends with four live songs. There's two originals, a cover of an Elvis Presley classic and a reworked version of one of the band's most underrated songs, 1994's "Pincushion." The protagonist of this new version seems to be more of a punisher than the punishee found in the original version, and accordingly the song's title has been changed to "Sinpusher."

"I do believe one would say, it's 'push came to shove'," Gibbons explains when asked how the song's evolution took place. "It’s the collective retake on that very special one everyone liked, and the decision arrived … 'Go another!'"

So 15 years later, which tracks from XXX hold up best in his memories? "We’d have to include 'Fearless Boogie' on the list — it’s been included in our recent collection The Very Baddest of ZZ Top.' We’re also fond of 'Hey, Mr. Millionaire' on which we’re joined by our great friend Jeff Beck and, yeah, that bad, bad 'Sinpusher' and, of course, '(Let Me Be Your) Teddy Bear' because without Elvis, we wouldn’t be having this conversation, would we?

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