When Natalie Merchant was a twenty-something chanteuse fronting 10,000 Maniacs, she was every nerdish schoolboy's crush. With her unadorned voice, intelligent lyrics and librarian chic, Merchant broke a few million hearts and spawned the Lilith Fair generation in the process. Her decision to go solo in the mid-'90s didn't change much: The music became moodier and more worldly, but the singer's serious approach remained locked in place, undoubtedly to the chagrin of her record label. Though Merchant's 1995 debut, Tigerlily, was a five-million-selling smash, 1998's Ophelia and last year's Motherland haven't come close to that number. Thus, her recent tour with superbore Chris Isaak smacks of a Stingly career move toward the middle -- a chance for aging concertgoers to let down their hair and wave their Chardonnay like they just don't care. This might not be an entirely bad thing. Merchant might be the Miss Manners of pop, but in an era when schoolgirl strumpets and poperatic divas rule the airwaves, her prim presence seems like a giant fuck-you to the mainstream. Merchant's cool precision and matronly aura got her labeled a priss from day one, but those familiar with her live performances know she sheds the schoolmarm routine and gets down to the more serious business of having fun.