“Even before the introduction of the formal feast of Christmas, Christians sang the Angels’ Hymn (Gloria in excelsis Deo), and hymns and lyrics in honour of Christ’s birth appear with regularity beginning in the fourth century. The earliest known Latin hymn for the season is credited to Bishop Ambrose of Milan: Veni redemptor gentium (‘Come, Redeemer of the Nations’). The fourth-century poet Prudentius penned several lyrics taken up as hymns in the Latin liturgy, including Corde natus ex Parentis (‘Of the Father’s Love Begotten’), Quid est, quod arctum circulum (‘Why Doth the Sun Re-Orient Take?’), and Quicumque Christum quaeritis (‘Lift Up Your Eyes, Who’er Ye Be’). In the fifth century, Caelius Sedulius wrote the memorable lyrics A solis ortus cardine (‘From Lands that See the Sun Arise’) and Hostis Herodes impie (‘How Vain the Cruel Herod’s Fear’), both of which, like all of these early Latin hymns, would be used not only in the medieval Church but, in translation, in varied Christian denominations up to the present day.
“As the Roman-rite cycle of feasts and seasons settled, so too did the musical foundations that would give it character and expression. By the eighth century, on the seven days leading up to Christmas Eve, most liturgical communities in the West adorned the chanting of Mary’s canticle at Vespers, the ‘Magnificat’, with one of seven or more special antiphons known as the great ‘O’ antiphons. Each opened with an apostrophic invocation of the still distant Jesus by one of his titles or characteristics drawn from Old Testament prophecy: O Wisdom (O sapientia), O Lord and Leader (O adonay), O Root of Jesse (O radix Iesse), O Key of David (O clavis David), O Radiant Dawn (O oriens splendor), O King of All Nations (O rex gentium), and O Emmanuel (O Emmanuel rex). After the invocation and a short elucidation of its image, each ‘O’ antiphon ended with a longing petition for Jesus to ‘come’ — to teach, rescue, shine, or save mankind. All seven antiphons were sung to the same unique, six-phrase melody; they were often accompanied by the church’s largest bell; and they were typically sung by the most prominent members of the liturgical community. This festivity heightened the sense of anticipation on the final days of Advent and started a liturgical crescendo that would peak with the special festivities of Christmastide. Their performance instructions illustrate that it was not just what was sung but how it was sung — the manner of its performance — that made the Christmas season stand apart in the music of the medieval Church. This how comprised many different factors (including who, when, and where) that varied according to a feast’s or season’s festive rank and nature.
“The Christmas Day liturgy of the Royal Abbey of St-Denis outside Paris, resting place of most of the French monarchs of the Middle Ages, illustrates many of the ways that even unison chant performance could be heightened to reflect the solemnity of Christmas. The abbey’s first surviving ordinal, or instruction book, indicates that its thirteenth-century monks celebrated Christmas with a level of musical festivity in some ways even greater than at Easter, the ‘feast of feasts.’ In the special night Mass that followed the night Office of Matins on Christmas Day, for example, all the abbey’s bells sounded from the beginning of the Gloria in excelsis to its end. This emphasis on the Angel’s Hymn — withheld from the Mass throughout the penitential season of Advent — highlighted its joyous return on the actual anniversary of the blessed night ‘when the angels inaugurated the custom.’ . . . The abbot himself was to sing or intone some of the day’s important chants: the eighth responsory and the reading of the Genealogy of Christ at Matins, and the special antiphon for the Benedictus canticle at Lauds. During some of the chants of the Hours, the community was to kneel for mercy. Two priests censed not only the altars but the entire community throughout the singing of Matins. All monks were to be ‘festively dressed’ in their finest vestments. Some chants of the main Mass were to be sung from precious ivories, likely ivory diptychs that could hold a sheet of parchment, and other precious relics, vessels, and objects were carried in the day’s music-filled processions. Some chants, too, were to be sung in especially sacred places: the abbey’s former and current sancta sanctorum, both associated with the abbey’s patron saints and royal benefactors and reserved only for special moments on the highest-ranking feasts. Before the cantors intoned the Christmas Introit Puer natus est (‘A Child is Born’) to start the main Mass, for example, certain ‘prepared monks’ sang the three introductory verses (tropes) beginning Hodie cantandus est from the abbey’s current Holy of Holies in the raised, twelfth-century chevet. In this same space, ‘someone singing well’ was chosen by the cantor to chant a rare antiphon before the Gospel. These colourful instructions show that then, as now, Christmas services required the best singers and careful preparation. In many medieval centres, as at Notre-Dame in Paris, strong soloists might introduce polyphony, or multi-voice music, at the highest moments of solemnity.”
— from Tova Leigh-Choate, “Carols and Music to 1900,” in The Oxford Handbook of Christmas, edited by Timothy Larson (Oxford University Press, 2020)