The Welsh words that Alice gives are the ones sung over here. (I quite liked the English translation, too) Suo Gan is *lullaby* (ie a whispered song - the wind can *suo*)... and initial consonants *mutate* but, trust me, you don't want to know the rules! It isn't particularly connected with Christmas here, but see below. I have quite a nice arrangement for female choir ...
An anecdote: when it *aired* in Empire of the Sun, I helped investigate it for a Welsh current affairs programme and had a real run-around. I think it was distributed by ... Warner Bros? ... and the people in the London office were crazy about the song. But they thought it was Japanese. (Typical.) We ended up phoning the New York office: Spielb. was off somewhere and no one there had a clue. So, our musicologist figures it's one of two things...
1. He picked it up from a well-known instrumental recording by the Halle Orchestra WHICH, I believe, is a track included on some Christmas compilations. So there is a connection ...
or...
2. He picked it up as a hymn tune. Our Musicologist says that it was used as a hymn tune in some parts of the USA, although I never came across it in Canada. This sounds like a tie-in with the Hymn Book discussion...
sian