I first heard an arrangement of this plainsong hymn about twenty-five years ago. It remains a favorite, though I’ve yet to muster the nerve to introduce a new congregational piece during the Christmas season.
Of the Father’s love begotten,
Ere the worlds began to be,
He is Alpha and Omega,
He the source, the ending He,
Of the things that are, that have been,
And that future years shall see,
Evermore and evermore!
I couldn’t find a pure chant version, but the young people in the video do a creditable job with an understated arrangement.