“Advertisers are harnessing pop’s powerful potential for cross-branded synergy more aggressively and variously than ever. One side effect: Commissions for original music for ads are down, and licensing music from established and emerging artists is through the roof, marketers say. It’s a mixed blessing that can introduce underground artists to a wider fan base. But just as often, ad pop adulterates musical chestnuts and can distort a song’s original intent.” And oh, the fans might object…