I've noticed that as I stream music through Apple Music the songs are caching (I think maybe?) and storing on my iPhone. They don't seem to be locally storing themselves but they are eating up my memory. As a test I deleted all the music off my phone and streamed for a day. Before streaming I had 0 songs, after the day was done I had roughly 50 songs taking up memory. If you go to the 'About' section of your phone you will see how many songs are being 'stored'. I found that if I sign out of my iTunes account and sign back in it wipes the music. This seems to be happening to all my iOS devices, wondering if anyone else is noticing this as well?