ZZ Top ended their 2005 Whack Attack tour with lime-green jackets, white-fur guitars and a hundred minutes of streamlined boogie at New York's Beacon Theater on Friday night. At one point in the show, the second of a two-night stand, guitarist Billy Gibbons, bassist Dusty Hill and drummer Frank Beard paused to toast their crew with glasses of champagne. (The roadies presumably got their swigs after the gear was back in the trucks.)

This was a big night for everyone, though, especially the crowd. It's a rough guess, but the last time the biggest little band in Texas made this much noise in a room this small was probably in the waning days of the Nixon administration. And in this intimacy, it was possible to see and hear in extreme close-up why ZZ Top are, under the rabbinical facial hair and Eighties-video comedy, a great electric blues band, authentic in their passion yet devious in their simplicity.

Gibbons' soloing, in particular, was a renewed revelation: unretouched psychedelic skid and snarl, with just a few notes in each phrase but every one armed with maximum torque and articulated bite. His breaks in "Jesus Just Left Chicago" and "Brown Sugar" (the original on ZZ Top's First Album) were at once precise and unhinged, models of concentrated overdrive. In a cover of Muddy Waters' "Catfish Blues," Gibbons took off with nothing more than heated hammering on a single note, which -- just as you thought he was going nowhere else -- exploded into a dazzling series of controlled-feedback shrieks and razor-wire curls: Jimi Hendrix-style lightning honed to lethal effect.

Shtick came naturally to ZZ Top -- as far back as 1976, when they toured the U.S, with an entourage of Lone Star flora and fauna (cacti, a buzzard, longhorn cattle). But the real devilry was in the musical details, and those twists jumped out of tonight's din: Gibbons' and Hill's synchronized guitar-bass spins in "Got Me Under Pressure" and "Waitin' for the Bus"; the rhythmic turnarounds in "I'm Bad, I'm Nationwide" and "Heard It on the X"; Beard's tumbling drum break into Gibbons' tearaway key-change solo in "La Grange." A closing threesome of "Gimme All Your Lovin'," "Sharp Dressed Man" and "Legs" from 1983's mega-platinum Eliminator showed how easily ZZ Top adapted their allegiances to Albert Collins, Freddy King and Lightnin' Hopkins to dance-floor zoom, while a paucity of material from recent RCA albums seemed to acknowledge the band's struggle to improve on that modernism, at least in the studio.

But at the Beacon, there was no denying the immensity of the basic math that is ZZ Top: "the same three guys," as Gibbons told the audience early in the set, "playing the same three chords for thirty-five years."