Read in my ebook you have VIP
-use mechanism from ebook to protect your app
-do not use just "mp3 downloader" in your title, add some word for example "Pro Mp3 Downloader"
-if you have illegal source of music, when sending it, disable downloading feature for some time
-add notification for moderator about music source and creative common v3
-add links to creative common v3 licence
-leave DMCA information about contact