Hi Catfeet,
Assuming my assumption above was correct, the carol I'm thinking of is variously known as "Gabriel's message" and "The Angel Gabriel". It's a Basque carol collected and translated by Sabine Baring-Gould. Maddy Prior does a great version (I think that's tautological actually, she's never done anything that wasn't) with the Carnival Band on "A tapestry of Carols". I couldn't find the lyrics in the DT but they are given here if you are interested.

Pete M