After analyzing 12,445 tracks played on Beats 1 from July to August, Quartz finds that the streaming radio station has a genre bias:
Though Beats 1 is an eclectic mix of genres, some listeners have complained that it plays too much hip-hop. “Too much” is a matter of taste, of course, but looking at the breakdown, there is indeed more hip-hop than anything else in the repertoire. (These are the genres as iTunes defines them. Crucially, the dataset only includes genre for about half of the songs.)
A close second— Alternative, followed quite a ways back by Electronic, R&B/Soul, and then Pop. "Just edgy enough to not be called mainstream," sounds about right to me.