Less than a week after the public release of iOS 8.3, Apple has already begun the developer beta cycle of the next iOS update, with the release of the first iOS 8.4 beta to registered developers. As expected, iOS 8.4 appears to focus primarily on a redesigned Music experience to pave the way for Apple’s upcoming streaming music service, with a number of significant changes to the built-in Music app, paralleling some iTunes features such as Now Playing, Mini Player, and support for adding to and managing the Up Next queue.
The Music app redesign is apparently being overseen by Trent Reznor, the creative head at Beats Music, who has reportedly been working on a secret project at Apple since at least last fall. This first iOS 8.4 beta, featuring a build number of 12H4074d, is also accompanied by an Xcode 6.4 beta to support the new APIs and development environment, and notes about a dozen limitations with the new Music app at present.
It is expected that most of these are just issues related to the new Music app not being entirely finished in this first beta, and the app experience should improve through the remainder of the beta cycle.