Aselin Debison's recording -- often played on radio in the last few years -- has the line as "Now the gift-giving service was coming," not "... Christmas eve service ...".

She also very clearly and precisely sings " ... the very first nightingale's song," not " ... nightingale song."    (This makes more sense to me, because I gather that the implication is that this was the song of the first nightingale, not just the first time one ever sang.
And, yes, I know, nightingales were probably around -- singing, even -- before people started celebrating the birth of Jesus with church services, but let's suspend disbelief long enough to enjoy a good story. ) : )

There are a few other minor variations between what's posted at Stephanie Davis's website and the way Aselin Debison sings the song.

Lyrics printed in liner notes and on songwriters' own websites are not always 100% accurate. Sometimes they leave out words - even key words. Just the kind of errata that can occur when a book is published. Note that half of the punctuation is missing from the lyrics you found at Stephanie Davis's website. It doesn't mean there shouldn't be periods at the ends of sentences, just because whoever typed up the lyrics omitted them. : )

I don't think minor variations such as "whose beauty was fit for a king" vs. "for its beauty was fit for a king" [Aselin Debison's version] or "to that cascade of notes" vs. "to the cascading notes" really matter. But there IS a difference between "nightingale" and "night in Gale." (Cf. one of the other threads about this song.) *g*