Here are some “O Antiphons”, chanted at evening prayer for the 8 consecutive days before Christmas
http://www.godtube.com/watch/?v=JF2MCJNU
also there is another advent piece called “Ye Clouds of Heaven” - can’t find a youtube version as of yet but the refrain is as follows:
Ye clouds of heaven open wide,
and once again this advent-tide,
Rain down the Savior from above,
Who comes to teach His way of Love.