Hello, everyone. I am looking for a song that I used to sing with my choir in a concert. I have searched all over the place but I cannot seem to find it. It is an arrangement of Agnus Dei. Unfortunately I do not know who it is composed or arranged by. I also barely know how to read music and don't remember much except the lyrics and how the parts go; I sang it a long while ago and we were all pretty much beginners so I can't give you much information regarding that but I will describe the song to the best of my ability.

There were 3 parts (or at least, that's how we sang it): Soprano - Alto - Baritone (I think, there weren't many guys so while they were mainly baritones, occasionally they would have other parts, but I think this one is Baritone)
The accompaniment: Piano
Lyrics went exactly like this
(Everyone together):
Agnus, Agnus Dei
Agnus, Agnus Dei
Agnus, Agnus Dei (everyone would drop down to lower notes right here)
Agnus, Agnus Dei (same lower notes)
Agnus, Agnus Dei (it would return to how it sounded in the beginning right here)

Lamb of God, you who take away the sins of the world, have mercy on us, miserere nobis (I believe the guys had the melody on this part)

Then everyone would sing "Agnus, Agnus Dei" again but instead of singing together, everyone had their own separate parts.
-The sopranos would sing first and I believe it sounds exactly like their first part
-The altos would come in immediately after the sopranos sing the first "Agnus" in "Agnus, Agnus Dei"
-The baritones come in after the altos sing the second Agnus in "Agnus, Agnus Dei" and also they don't sing the fifth one, they instead go up to higher notes twice on the fourth "Dei" and then hold it until everyone else gets to their last "Dei"

(Back together again, with the guys getting the melody):
Lamb of God, you who take away the sins of the world, grant us peace, dona nobis pacem

Then everyone hums the letter m until the song ends

I know it may be confusing and I'm sorry about that. If you need any clarification on anything please let me know. I have been looking for this song for awhile and I really want to find. Please help in any way you can (score, arrangement, a recording, etc.). Thank you in advance for any help.