Glory be to God on high, and in earth peace to men of good will. We praise thee, we bless thee, we worship thee, we glorify thee, we give thanks to thee for thy great glory:
O Lord God, heavenly king, God the Father Almighty;
O Lord the only begotten Son, Jesu Christ;
O Spirit and dear advocate of orphans.
O Lord God, Lamb of God, Son of the Father, First-born of Mary the Virgin Mother, that takest away the sins of the world, have mercy upon us; thou that takest away the sins of the world, receive our prayer to the glory of Mary; Thou that sittest at the right hand of God the Father, have mercy upon us.
For thou only art the Holy One, making Mary holy; thou only art the Lord, ruling Mary; thou only, O Jesu Christ, art the Most High, crowning Mary, with the Holy Ghost, in the glory of God the Father. Amen..
For your interest, I have laid out the Gloria in excelsis Deo in an adapted-Cranmer translation, as it was appointed to be sung or said on feasts of our Lady in the Rite of Sarum. I have entered in red the additions made therein to the basic text. This sort of text is called 'farced', and was, I believe, mentioned at the Council of Trent as an example of liturgical corruption! Until at least the time of Leo XIII, that is, comparatively recently, the Missal of S Pius V still retained a rubric specifically indicating that the standard text was to be used even on feasts of our Lady! (Does the removal of this rubric mean that the Marian version is now debanned?!) Personally, I find these additions not unattractive, particularly in the last paragraph.
But you will be panting to point out to me that the first interpolation is nothing to do with the Mother of God; it serves instead to import the Third Person of the Blessed Trinity in a clause perhaps suggested by the Magnificat Antiphon on Ascension Day. It is designed to 'complete' the parallelism with the references to the other two Persons. Indeed, some earlier texts (Codex Alexandinus; Bangor Antiphonary) had also squeezed the Holy Ghost into this part of the canticle. (It has to be admitted that this trinitarianisation of the first part of the Canticle results in imposing upon the whole formula quite a different structure from that of the unfarced text.)
Understandable. People felt they ought to import the Holy Ghost into more or less everything, as soon as the Dogma of His Divinity had been articulated and Defined ...
... oops! I misspoke. I'd better withdraw the objectionable and improper implication that the Dogma was a novelty. I do withdraw it unreservedly. But I'll explain in part (2) how I came to make such a mistake.