— silent night:

http://www.pianolessons4children.com/songs/silent-night.php

http://makingmusicfun.net/pdf/sheet_music/silent-night-piano-easy.pdf

— Canon in D

http://www.8notes.com/scores/420.asp – simple, short, with a matching audio

https://www.youtube.com/watch?v=mHYbdfWEIiA is good piano recording