It's not easy to play rippling rhumba triplets in the right hand against a driving, eight-to-the-bar boogie in the left--but San Francisco's Mitch Woods plays it as well as anyone outside New Orleans ever has. On the title tune from his fourth album, "Shakin' the Shack," Woods knocks out that riff with a precision that renders its pleasures contagious. The whole album, in fact, is devoted to the infectious joys of boogie-woogie, whether it be delivered New Orleans style, Kansas City style, Chicago style or California style. This may be complicated music to play, but it's very easy music to hear. Sax players Jonny Viau and Michael Peloquin add a punchy fullness that makes this album Woods' best. Woods is only a so-so singer (he has particular trouble selling ballads), but he's such a special pianist and bandleader that it hardly matters. He wrote all but one of the songs, but the whole album is rooted in the mid-century origins of boogie-woogie, a tradition that Woods carries on in vigorous --Geoffrey Himes