The big streaming dogs are in a cat fight. Spotify first slammed Apple Music recently, saying the company is using its App Store approval process as "a weapon" and "insisted that Spotify use Apple's billing system if it planned to sell subscriptions," according to BuzzFeed. But Apple has hit back with a new letter from Apple general counsel Bruce Sewell, sent to Spotify general counsel Horacio Gutierrez, to rebuttal the allegations.

"We find it troubling that you are asking for exemptions to the rules we apply to all developers and are publicly resorting to rumors and half-truths about our service," Sewell wrote. "Our guidelines apply equally to all app developers, whether they are game developers, e-book sellers, video-streaming services or digital music distributors; and regardless of whether or not they compete against Apple. We did not alter our behavior or our rules when we introduced our own music streaming service or when Spotify became a competitor."

Read the full letter here.