Rockabilly's endurance continues to defy those who regard the genre's resurrection as more of a fashion statement than a musical movement. While you'll probably see less gingham and grease in local clubs these days, interest in rockabilly's rabble-rousing sounds remains solid. Big Sandy and His Fly-Rite Boys, Friday, December 1, at the Bluebird Theater with the Blue Ribbon Boys, are a fine example of why this music continues to please: The Southern California five-piece led by the amiable, appealing Big Sandy (né Rusty Williams) approaches it with a dexterity and musicianship that makes the stuff look easy. While Sandy's sound -- a kind of retrobilly fused with a big-band flair, peppered with occasional excursions into country, swing and even calypso -- is certainly rooted in nostalgia, there's a timeless quality to it. It could be the band's smooth, almost seamless delivery, or the way the tunes make you want to take to the dance floor. Then again, maybe it's just Big Sandy's big ol' smile.