I just moved the "eXemplify" notification sound from Xperia Z3 to the Xperia 1. I converted the sound to an .mp3 file (320CBR) first.
After adding the file I got a notification "adding the sound failed". Then I renamed the file to "exemplify2.mp3" and then got added to the list and worked, but I still got the "add failed" notification. I don't know what was the reason for the "failure" if the sound was added and works?