You are purchasing a custom made arrangement of "Ding Dong Merrily On High" Inspired by Celtic Woman. This is a choral arrangement for SSATB and full Orchestra which includes, keyboard, guitar, strings, percussion and horns as well as all vocal parts. This is in the same key as the original and very similar.
There is the piano/vocal edition only available as well at this link:
The Video is of the Angel City Chorale in Los Angeles performing this arrangement