"It's not like I'm out there just singing a silly little song I don't care about and shaking my ass," says Chan Marshall, aka Cat Power, the Georgia-bred outsider-artist-in denial.  With an uneasy sotto voce warble and chronic stage fright that makes every show a psychological death match, she has become alt-rock's dysfunctional Sade, making comforting music about feeling uncomfortable.  Last year's The Covers Record deconstructed songs by the Velvet Undergound, Smog and the Rolling Stones, and another volume of covers is already in the works (with Mary J. Blige's "Deep Inside" on the short list.)  But the indie-rock heroine's main concern is recording the follow-up to her last set of originals, 1998's plaintive Moon Pix.  "There's going to be a lot more shit going on this one," says Marshall.  "All of my other records were recorded in three days.  This time I'm going to be in there for three weeks."