Apple Music Artist Radio Stations

I enjoying listening to radio stations that are based on an artist (e.g., Nat King Cole or Ella Fitzgerald) and I have noticed that there seems to be a wide definition of "similar artists" (e.g., Josh Groban, the Ronettes and Stevie Wonder show up a lot on these two stations). Also, I get a lot of Christmas music from these similar artists, despite the fact that it is July. I don't want to "dislike" these other artists or genres - they are appropriate in their own stations. I realize there are licensing concerns to be factored in, but how can I train my stations better? I want to stick with Apple, but Pandora seems to get me a bit better.