This is a 1000 year old song about Mary.

The score is here: https://gregobase.selapa.net/chant.php?id=23

The first note is “So” (solfegge version of G, singers will know what I mean) and So is Eb (Do is Ab.)

A great sign appeared in heaven: a woman clothed with the sun, and the moon under her feet, and on her head a crown of twelve stars.

Sing ye to the Lord a new canticle: because He has done wonderful things. Glory be.