Par. 28.118 "Hosanna"
The glorified spirit of Justinain sings this hymn. The authors of the Gospels were protrayed as four different creatures: Matthew as man, Mark as lion, Luke as ox, and John as eagle. "Hosanna, holy God of hosts who by thy brightness dost illuminate from above the happy fires of these realms." We see it fitting that in Paradise we sing hymns of joy
Par. 23.127 "Regina Caeli"
"Regina Caeli" is sung in the Heaven of the Fixed Stars. "By nature with superior honors graced, as gem of gems above all others placed" For this being Mary, we can assume that the gem color is Sapphire and it also being the exact shade of the air or atmosphere in the climate of Rome. If we think of the term "Fixed Stars" we see the focus on Mary and how the angels surrounding God have been struck and mesmerized without distraction of that around them. (DR)
Par. 27.1 "Gloria Patri"
In celebration of the completion of Adam's "educations," they sing the Gloria to the Trinity. The host of souls seen in the eighth heaven now sing the Gloria Patri. "Glory be to the Father, to the Son, and to the Holy Ghost. As it was in the beginning, is now, and ever shall be, world without end." If we see the interpretation of these words following Dante's brilliant passing of his entrance examination. This hymn is used as a doxology, which mean a short prayer or hymn of Praise to God. This hymn can be understood as glorifying God in prayer as we3ll as addressing the Holy Trinity (Father, Son, and Holy Ghost). As it was in the beginning is now and ever shall be is interpreted as the eternal nature of God. He was there before time began and he will be there when time ends. He never changes.