A friend of mine needs an accompaniment for the Magnificat antiphon, Hodie Christus Natus Est. (Benjamin Britten used this antiphon - and altered it somewhat - in his A Ceremony of Carols.)

Certainly there must be a collection of chant accompaniments now in the public domain which contains this chant, which is found in both The Liber Usualis and the Antiphonale Monasticum, as well as other sources.

Thanks.