Apple has released a new beta version of iOS 8.4 to developers. They have also released the first version of the beta for their AppleSeed testers.
The latest beta of iOS 8.4 can be downloaded from Apple's iOS Developer Center, as well as over the air on devices running the previous beta. Developers can also download the latest release of the Xcode 6.4 beta.
The first beta version of iOS 8.4 was released earlier this month. The biggest notable change was the inclusion of a revamped Music app, which included a more streamlined version of iTunes Radio. This is the second major update to have its preview pool expanded beyond developers. Apple started utilizing their invite-only AppleSeed program to test iOS 8.3 with select users in March.
Thanks to Keith for the tip!