TrueAnthem, an ad-supported music download service, is branching out into the world of ad tracking. We’ve always had some reservations about TrueAnthem’s service. The San Francisco-based startup works mostly with small, unsigned artists and has them read spoken ads in front of their songs, which really ruins the listening experience — at least for me. But it’s managed to sign up several big brands, like Nestlé, to its service. Now it’s providing tools to those brand marketers to help them track the performance of their viral campaigns.