Getting back to the New Living Parish Hymn Book, a had resolved to do every hymn come what may, but this one is a bit much.
It is Joseph Gelineau’s setting of Psalm 50 (51). Nothing wrong with that, but with the date of publication, the original Grail verses are used. I also have the version in Gather 3 which has revised Grail and needs to put extra music in some verses to cover the amendments. There are ten verses, upon which I refuse to attempt a metrical conversion.
Having refused that, here is a backing for the Antiphon:
Have mercy, Lord, cleanse me from all my sins.
Hymnary have a preview of the sheet music from Catholic Book of Worship III.
This is pretty:
Not Gelineau but fascinating: