Downloading Ringtones ???

I know this is a stupid question but how are you supposed to download music ring tones now ? In an older version of i-tunes there would be a little bell symbol next to some of the music I purchased that would allow you to create a ring tone. Now that feature does not exist in i-tunes. I tried going to the AT&T site and it says that you cannot download ring tones for the i-phone on their site either and there is nothing I could find in the App store. Can someone please tell me how to download music ring