This is a short piece of Christmas music, setting a text by the brilliant and sadly late crossword setter, Araucaria (the puzzles of whom always defeated me). I have set both the text and the anagram shown here:
While shepherds watched their flocks by night, all seated on the ground
Hark the herald angels sing the boy's descent, which lifted up the world!
The anagram ("Hark the herald...") is given to the soprano, alto, and tenor, over a "ground" in the bass, which sings "While shepherds...". The ground or cantus firmus is based on the opening of the tune Shaw Lane, traditionally used for this carol where I live in Todmorden, West Yorkshire.
It would not be fair to write a tribute to a master crossword-setter without a musical equivalent to a play on words, and therefore the "ground" is palindromic.