Katy-Gaga story tease

SIRENS WAIL: When two megastars of the Pop world roll out singles at the same time, that's a story. Katy Perry's "Roar" and Lady Gaga's "Applause" are making big noises in the marketplace ahead of their Q4 album releases. How are their singles and album preorders stacking up? We do a head-to-head comparison here. (8/27a)