On this great feast of the Immaculate Conception, we began by singing the Introit (Gáudens gaudébo), rather than a hymn, as the processional. On a Sunday, we would sing the Asperges, and the Introit is sung after the Asperges. But since today was not a Sunday, the Asperges is not sung, and thus we could start right in with the Introit.
During Advent and Lent, normally, Father would wear violet vestments, we would sing Mass XVII, there would not be a Gloria, and the organ would not be used. But today was a feast. Father wore white; We sang Mass IX in honor of the Blessed Mother; We sang the Gloria,and the singing was accompanied by the organ.
We paired Credo III with Mass IX. After the Credo, Father opened the tabernacle and exposed the Blessed Sacrament so that we, the faithful, could make our consecrations to Jesus through Mary after our 33 days of preparation. We preceded this with the Veni Creator, which is customary on such occasions.
At the Offertory, we sang the ancient hymn, O Quam Glorifica.
At the Communion, the mixed choir sang a very beautiful two-part setting of Tota Puchra Es, which is based on the Song of Songs and begins, Tota pulchra es, Maria. Et macula originalis non est in te (Thou art all fair, O Mary, and there is no original stain in thee). These exact words are the versicle in today’s Alleluia. (You can hear a nicely executed recording of this by Harpa Dei at this link.)
The schola followed that with the solemn version of Alma Redemptoris. This is one of the four Marian hymns sung during compline, according to the season, and is the one that is proper to the season that goes from Advent through the Purification.
For the recessional, we sang the very fitting Immaculate Mary.