Welcome to Android Central! The Music apps (either the stock Music app or Google Play Music) will show all music files on your storage--including ringtones, since they're mp3 files (or possibly wav or ogg files). This only applies to ringtones that weren't preinstalled on the phone--so tones from Facebook and Hangouts might show up, as well as any custom tones you may have created or downloaded. It's a minor hassle. The problem is that you can't use the trick of adding a file called ".nomedia" in the directory where those tones are, because not only will they be hidden from the Music app, but they'll also be hidden from the system if you actually want to set one of those tones for your notifications.