Want original text alert back.

[laserone]

Hi, I accidentally changed​ the notification sound on my Nexus 6. When I went to reset it back to what it was, the sound that I was used to was not in the list. Now I'm stuck with a notification sound that I'm not used to. I would really like to have the original notification sound back, the sound associated with text messages. Where would I find that on the phone? How do I reset that back to the way it was? Can download it? Thanks. (Still on Android 6.0.1)