OF all the lost causes in the pop music world, the most poignant may belong to the 3,500 fans who recently signed an online petition begging Britney Spears not to lip-synch on her coming tour. Ms. Spears, in keeping with the dominant star etiquette, has firmly denied the practice (''I don't lip-synch,'' she told a group of reporters by telephone last November). But no less an authority than her manager, Larry Rudolph, begs to differ. He said in a phone interview that Ms. Spears's tour will feature a mix of live and lip-synched vocals, and confirmed that past tours have included the same. ''On those numbers that are difficult, if not impossible, for her to sing completely live while she's performing,'' he said, ''what we do is we'll put a backing track which will support her.''
The practice of lip-synching is practically as old as recorded music. But now, after decades of derision and outrage, audiences are warming up to the fakery. In chat rooms and fan sites, Ms. Spears's petitioners have been shouted down by peers from around the world who not only don't mind a little gimmickry -- they prefer it. They may have no choice: live pop performances rely on an ever-more-intricate mix of live music, prerecorded sound and high-tech tricks, including new programs that produce the same flawless sound as a lip-synched performance, even if the person singing is jumping around, hanging upside-down or just plain out of tune.