If your name is Robert Williams, the obvious choice for a nickname is Big Sandy. How else to distinguish yourself from the countless other Robert Williamses in the phone book, especially the crooners operating California-based Texas-swing and rockabilly groups? Williams' Big Sandy & His Fly-Rite Boys works the kind of open-all-night vibe that keeps groups booked year-round, regardless of trend. Unlike the other swing revivalists of the past decade (the twang-free set), Big Sandy doesn't deliver its music with an ironic wink or play with minstrelesque broadness. The group's sound is also considerably tougher, though Williams says he's most comfortable playing in front of an audience that's dancing, dancing, dancing. The outfit's latest, It's Time, was recorded with vintage microphones and amps, and guitarist Ashley Kingman (nickname requested) plays a custom 1957 Magnatone, but the disc isn't hamstrung by gimmickry and reverence. Live, the group swivels and hammers with a ferocity that continually gets its music called various kinds of "slab" -- slab of rockabilly, slab of swing, meaty slab of roots music.