How do I copy a song sent to me via email or message to Music.app?, How do I copy a song sent to me via email or message to Music.app?

I've received a song via Mail (and then via Messages) on my iPhone 5 running iOS 6.0.2 and can't copy it to the Music.app. I am remote and want to listen to this song as part my library but can't seem to. I can however listen to the song on the phone as an attachment. Is adding to Music.app just not possible on the device?