Mobile music may be claiming a larger share of the overall digital music sector than ever before, but the trend seems to have bypassed Warner Music Group. Amid the results for its second fiscal quarter, which ended March 31, WMG reported that its revenue from mobile music products - ringtones, ringback tones and full-track downloads - fell 17.6% sequentially. According to a MocoNews post on the results, WMG's mobile music revenue dropped from $56.4 million in Q1 to $46.5 million in Q2.

That might all change in the future, though, if Warner keeps doing exclusive deals with the carriers. During the earnings call, WMG chief Edgar Bronfman crowed about the company's recent promotions with Verizon Wireless and Vodafone surrounding the new Madonna album "Hard Candy." As a result of offering the single "Four Minutes" a day before it was available anywhere, the song became Vodafone's best-selling track yet.