the player i was using was the stock Samsung Note 3 Music app. it refused to play iTunes files. perhaps it doesn't support AAC and only plays MP3?
I don't like Google Play Music as an app. it cannot be themed the way i like, has tons of gestures that i keep triggering by mistake, the UI is a mess, and so on. as such, i buy music that can be played or burned to a CD or used any way i want. besides, i got bitter after i got overage charges and noticed that Play Music had somehow chewed through 1GB of data and the app never shut down when i backed out of it. i still remain a proponent of an exit option in apps myself to avoid unwanted data use. on my G2, i also prefer the stock LG music app not taking over my lockscreen wallpaper. it shows a tiny version of its rather nicely done brushed aluminum widget and my lockscreen stays the way i like. that's another poor decision from Google. who wants their lockscreen wallpaper randomly changing to blurry album art?
When a song i bought on Google Play (someone told me that it worked differently than AA subscriptions and came as an MP3) wouldn't show up on the stock Samsung player, and i couldn't find it even after root (at the time i rooted to try ROMs and came back to TouchWiz unsatisfied with stock android) despite looking in /data/app and so on, even coming up empty in a search, i assumed they were some odd format. Point is though, root should never be needed if i BOUGHT the song, and chose to play it in an app that Google doesn't like. I am not some fanboy who thinks Google's decisions are all right. they just want me to use their limited, gesture ridden, and unthemeable app that chances design every time Google bats an eye. i'm a person who, when satisfied, doesn't need something to change. a music app should remain familiar, not hide menus behind gestures, add songs to my library i never asked for, and cannot be removed, or place files in either an odd format, or hide them in a folder i can't find.