The New Oxford Book of Carols has an interesting, new and improved setting for In the Bleak Midwinter, incidentally, in addition to the customary Holst tune known as Cranham. NOBC also has an "El desembre" version of the Catalán text in question, with their own translation, but the copious notes don't explain the "Lo/El" thing. Is there a difference of meaning or is it just a matter of dialect?

Haruo