Part of the ordinary of the Mass is a hymn called the Gloria in Excelsis Deo. "Ordinary" in this context means that it is called for in the Mass year round. The only qualification is that the Gloria is one of those parts of the liturgy which is left out in the penitential seasons (Advent and Septuagesima through Lent). Nevertheless, we call it ordinary because, except for that one proviso, you can count on hearing it at Mass, whether it be a Sunday or a weekday, whether it be July, October, Epiphany, Easter, or whatever. It is not, in other words, a part of the Mass for which the text changes each week, as with the propers. It is part of the fabric of the Mass. All of that presupposes, admittedly, that one has the traditional liturgy in mind. The Gloria, as you can tell by the fact that we still refer to it by a Latin title, comes to us from the Church's Latin tradition. The Latin Gloria is a Latinization of the Greek hymn which was used even earlier. Saint Hilary of Poitiers, the great fourth century bishop who became known as "the Athanasius of the West" and who was instrumental in the life of Saint Martin of Tours, is surely the man who gave us the Latin version. It is a beautiful hymn, and it is one of several surviving examples of parts of our liturgy which bears evidence of pre-Vulgate Latin. The use of the term "excelsis" instead of Jerome's "altissimis" in Luke 2 is a clear indication of this.
Anyway, this hymn merits being sung in our Church today on a regular basis, in either the Latin (where and when a given community or congregation is ready for it) or in a classic vernacular version. In the English speaking world, the version which is surely most deserving of that distinction is the traditional text of the Common Service (pages 17-19 in The Lutheran Hymnal).
One of the results of the modern LCMS trend of rotating Mass "settings" every season in a church is that the Gloria in Excelsis is kept away from our people even longer than we sometimes realize. Think about this. Your congregation is using Divine Service III before Lent, and then when Lent arrives, whether you are still using that order or not, you won't get the Gloria for a while, because it is not used in Lent. Then, when Easter comes, the decision is made to do "something special" since it is now the festive season of Easter, so instead of restoring to the Church's liturgical diet the use of this festive hymn, it is deemed better to use something else, maybe a Hillert hymn, maybe a Starke hymn, maybe something else. In fact, in some places, Divine Service III is reserved for Lent and maybe one or two other seasons, which means that when you finally do get around to the Common Service service, you won't hear that hymn. This is another reason I would urge the rethinking of the conventional wisdom of this liturgical rotation approach to worship. Liturgical diversity is afforded by tradition in many ways which do not impede on the use of the venerable Ordinary, such as using a variety of musical settings, the healthy use of propers, etc.
I share with you here a singing of the Latin Gloria. This video shows that it is possible for a congregation to learn to sing it. (Just to add a rubrical opinion, I do not agree with the priest and his assistants in this video sitting down during the Gloria; I know why they do it in that rite, but it is not something which I would see as needful, as a traditionalist Lutheran.)
This next video shows how it sounds when sung by a good choir:
Here is an Episcopal church doing the Healey Willan setting:
Finally, I found a YouTube video which does a nice job of capturing clearly the singing of the Common Service version (from LSB's third Mass order). And since I put in my respectful two cents' worth about a rubrical matter in one of the videos above, let me add here, that even though I don't condemn this per se, and even though I fully know that there may be any number of pastoral/historical reasons for it, that just for the record, I do not endorse a couple of things you will see in this video, namely, the celebrant wearing a surplice instead of mass vestments, the use of a white linen over the vessels instead of a traditional chalice veil, and the use of a decidedly noncrucifix behind the altar. Nevertheless, this is a Lutheran church, in Canada I believe, where the singing of this hymn is done clearly and reverently, and I appreciate the video: