updated 02:45 pm EDT, Mon July 29, 2013
Update likely to go live in September
(Updated with Apple TV 5.4 seed 3) In tandem with iOS 7 beta 4, Apple has also started seeding beta 1 of iTunes 11.1, reports say. The beta includes hooks for iTunes Radio, Apple's upcoming music streaming service. The service is slated go live around the same time iOS 7 is released, likely this September, although people will be able to listen via both iTunes and iOS.
Rather than allow listeners to play individual songs and playlists, as with Spotify, Apple has opted to make iTunes Radio a Pandora-style service where selected songs, genres, and artists are used to seed auto-generated stations. Likewise, people can vote on tracks to improve a station's quality and consistency. iTunes Radio will be free but ad-supported for most users; iTunes Match subscribers will get the ads stripped away.
The v11.1 beta is available for US developers through the Developer Center.
Update: Apple is also providing seed 3 of Apple TV 5.4. The code fixes problems with music skipping or failing to start over AirPlay, an iTunes Radio glitch that could cause an Apple TV to crash, and sudden dramatic AirPlay volume increases. iOS 7 can now be used to set up an Apple TV after restoring or resetting the unit.