After the penitential rite, we are reconciled with God and each other. (This assumes we are not in a state of mortal sin before Mass). Our hearts should be overflowing with joy and with gratitude to our generous and merciful God. What better way to express this than in song! St. Paul tells us "….to sing psalms, hymns and inspired songs"; St. Augustine said, "To sing belongs to lovers." is indeed a song, a canticle, of praise. There are many examples of such canticles in the Bible: Mary's (Lk 1:46-55), Zechariah's (Lk 1:68-79), Simeon's (Lk 2:29-32) which are used in the Liturgy of the Hours at Evening, Morning and Night Prayer respectively; others are found in Judges 5, 1 Samuel 2, Philippians 2, Colossians 1, et.al. (Let us look through your Bible and see if you can find more!) So, as we sing the "Gloria" we join people of the Old and New Covenant, Deborah, Hannah, St. Paul et.al. And we echo the angels who appeared to the shepherds at Bethlehem. Also in the Gloria are acclamations of praise; such acclamations have a longstanding liturgical history and we uphold this tradition. We continue with a petitions for mercy and conclude with a Trinitarian formula of praise. Note how often we use phrases that begin with the word "Glory…"; these are called doxologies (Greek - 'doxa'- glory, praise and 'logos' - speaking). By definition, a doxology is 'a Christian hymn or statement praising God' - a glory that is not ephemeral but very real and imposing! Let us then, with the Psalmist lift up our voices in worship and adoration and "sing praise to our God, for He is gracious; it is fitting to praise him."
(adapted and taken with permission from Anne Perez, Dir. Religious Ed., Holy Family Parish, St. Petersburg, Fla.)