THE TITLE of the new ZZ Top album, "XXX" (RCA), has several possible meanings. On the one hand, the three Xs are the Roman numeral for 30, and 1999 is the Houston trio's 30th anniversary. On the other hand, the title might represent an extra-strong Mexican beer or an especially salacious video. Guitarist Billy Gibbons, bassist Dusty Hill and drummer Frank Beard actively encourage all of these interpretations and more.

Whatever the title's implication, it's the first album from ZZ Top in three years, and it brings them to the Patriot Center on Sunday. The new disc carefully steers a middle course between the techno-blues approach of the band's best-sellingalbums, 1983's "Eliminator" and 1985's "Afterburner," and the stripped-down guitar-bass-and-drum approach of the last two albums, 1994's "Antenna" and 1996's "Rhythmeen."

" `Rhythmeen' was a purposeful excursion into restriction," Gibbons says. "We said, `Let's see what happens when we play just as a trio, no over-tracking.' That was fun, but this time we decided to take advantage of modern music-making devices. Some of them are so powerful and are so richly expressive that with a little bit of inventive tweaking they can be made to deliver really cheesy throwaway sounds."

Gibbons says this in an easy-going Texas drawl that is part put-on and part sideways approach to the truth. For the truth is that "XXX" uses state-of-the-art technology to recapture the cheesy keyboards, distorted guitars and booming drums of a '60s bar band. Of course, the same equipment allows those fuzzy tones to sound bigger than life, as if a Houston barroom had been enlarged into a basketball arena. Call it techno-cheese.

"This album is best characterized by the extremes of guitar tone that show up," Gibbons says. "We tried plugging in all kinds of effects, but that didn't seem to create anything radically different. The only thing left was to begin altering the instruments themselves. When we de-tuned the guitar two steps, that was interesting. Three steps down was devious, and beyond that we were into ZZ Top land. Who'd have thought a guitar would still be playable when de-tuned a full seven steps?

"The strings are like a boiling cauldron of spaghetti, but they do take on the craziest characteristics when slammed through the amplifiers. It's almost obscene what starts to happen. And that wasn't the only thing we did. The keyboard part on `Dreadmonboogaloo' is not an organ; it comes off a Roland groove box, which is basically a rap DJ's device. There's some bass synth tracks that follow Dusty's bass lines, which is something he brought to the party. Frank was ready with his fearless fistful of drum loops."

During the 1996-1997 "Rhythmeen" tour, the three musicians kept a notebook handy for any of them to scribble down a scrap of lyric, a chord progression or an idea about a song. When the "Little Ol' Band From Texas" reconvened to begin the recordings for "XXX," they pulled out the notebook.

"The collective notebook travels with us everywhere we go," Gibbons says. "It gets passed from bus to bus. Even the backstage, just-before-showtime idea gets jotted down. When we start recording, we go through the book page by page until something feels right.

"Dusty said we only need three chords to write ZZ Top music, so we shouldn't have three books; it'll just get too complicated. So we just have one book for the three of us. It's that 59-cent, spiral, well-ruled, lined notebook from the drugstore. We were tempted to go with the marble cover, but we went with the red."

"XXX" was originally meant to be a live album, but when ZZ Top started turning the notebook pages into songs and started playing with their techno toys, they couldn't resist the temptation to record eight new songs at their newly purchased mobile studio.

They did tack four live performances onto the end of the album. One is "Sinpusher," a version of "Pincushion" that evolved when the band couldn't remember the original lyrics. Hill gets to sing yet another Elvis Presley song; this time it's "(Let Me Be Your) Teddy Bear." The other two are previously unreleased songs, "Belt Buckle" and "Hey, Mr. Millionaire," the latter featuring an overdubbed appearance by Jeff Beck.

"We saw Jeff play live in New York," Gibbons says, "and backstage, I extended the rather brave invitation for him to consider performing on the ZZ Top work in progress. Mr. Beck explained that he generally doesn't appear anywhere but on his own records. But when I explained we didn't want him to play guitar but to sing, he said, `Well, I don't sing. It's a bloody brilliant idea; let's do it.' I said, `We'll record your vocal in a Texas hotel room just like Robert Johnson.' And that's just what we did."

The new album's liner notes contain a plug for the Delta Blues Museum in Clarksdale, Miss. ZZ Top has raised a lot of money for the museum, which this month moves into its new home, a renovated train depot on the railroad line that carried so many blues musicians from Mississippi to Chicago.

"I just visited the new facility," Gibbons says. "It's more spacious, but it still has a sense of history to it. It's where everyone went north from. If they weren't riding a train, they were walking. We're glad to do whatever we can for the museum. It's a small way of giving something back to an energy that has already given so much. The blues may be seen as a rather primitive art form, but it's been the cornerstone of some very complex careers."

There aren't many bands from 1969 that are still around in any form and fewer still with their original lineup intact. But ZZ Top -- two guys with beards on their faces but not in their names and one guy with a beard in his name but not on his face -- see no reason to quit.

"We've done this longer than anything else," Gibbons says. "If we wanted to do solo albums at this point, we'd choose each other as sidemen. So what's the point? Our second love is beating on hot rods. Body work is tough stuff; scraping your knuckles on an engine block is a lot harder than playing music. So the music seems like a vacation by comparison."

ZZ TOP -- Appearing Sunday at the Patriot Center along with Lynyrd Skynyrd. * To hear a free Sound Bite from "XXX," call Post-Haste at 202/334-9000 and press 8131. (Prince William residents, call 690-4110.)