Today is the third day of the misa de aguinaldo. That means we are six days away from Christmas. Before the 1960 rubrical changes raised the dignity and rank of the Advent ferias from 17 to 23 December, many countries in the Spanish realm kept the feast of the Expectation of the Blessed Virgin on 18 December, a holdover of the feast of the Annunciation transferred from 25 March by the Tenth Council of Toledo. Images of the Expectation of the Blessed Virgin usually depict Mary gravid.
The feast eventually assumed the title of Nuestra Señora de la O, literally, Our Lady of the O. What inspired Spaniards to use O traces a rather interesting history, which is ultimately, and surprisingly, choral in provenance. In summary, for seven days beginning on the eve of the feast, that is, from 17 to 23 December, at Vespers in the cathedral of Toledo, at the inchoation of the Great Antiphons, the dignity charged with the intonation prolonged the interjection O, and the rest of the choir joined with its lengthening, signifying with “these profound suspirations of longing” the “desire and yearning of the world for the Redeemer” . For more details, read this.
This same longing and yearning for our Saviour is echoed in the misa de aguinaldo, where the organ is pulsated (probably to the consternation of those not familiar with the tradition). “When Mary gave birth to the Word Incarnate, the gates of the celestial vault opened so that inextinguishable light of the Eternal Sun dispersed the gloom of the night. [… ] This is the principal reason why we sanctify the hour that separates natural darkness and natural light, in the days preceding the Nativity of our Lord. As the darkness distils into dawn, its unmoving emptiness fleeing from the rays of the sun, so we hearken not only to that hope with which our Fathers awaited the coming of the Messias, but also, and most importantly, to His return, prefigured by the sun rising faithfully in the East” .
“In the manner of the wise virgins, who kept a spare measure of oil for their lamps, we rise each day before dawn in the exercise of our holy faith, proclaiming our steadfast hope in His theandric love” in order “to express the impending jubilation that shall solemnly engulf Christendom on the day of His Nativity” .
Ut in omnibus laudetur Dominus.