Ars Technica has an article: Ringing up cash: ASCAP suing AT&T for ringtone “performance” - here is a quote:

“In the latest sign of just how confusing the music licensing system is, ASCAP is suing AT&T over the carrier’s sale of musical ringtones, looking for a cut of the revenue—even though the carrier is already paying for the download rights to these tunes. In a recent filing unearthed by the Electronic Frontier Foundation, ASCAP says that download payments aren’t enough because each ring constitutes a performance.”