I have long suspected the answer was that he learned them as a child in choir. Now I think I have the proof.
Lossius' Psalmodia was perhaps the most popular Cantionale of the sixteenth century. The copy of the edition I'm looking at was printed in Wittenberg back in 1594. There, we find a sequence for the feast of the Visitation, addressed mostly to Mary, but with a careful introduction explaining that this is a "salutation" and not an "invocation" and thus it is in the genre of Gabriel's greeting to the holy Mother and not in the nature of a prayer, which ought be addressed to God alone. The sequence (originally sung between epistle and gospel) is titled Ave, praeclara maris stella, and though Lossius attributes the text to Ambrose, it is generally recognized as having been composed by Herman the Lame, Abbot of Reichenau (d. 1054).
Here are some of the words from the text:
Te plenam fide, virgam almae stirpis Jesse nascituram, priores desieravant patres et prophetae. Te lignum vitae, sancto rorante pneumate parituram divini floris amygdalum, signavit Gabriel.
The fathers of old and prophets longed for you, faithful branch, to come forth at last form the generous stock of Jesse. Gabriel revealed that you, tree of life, moist with the Holy Spirit’s dew, God’s divine almond blossom would bloom. (p. 223).
There, in the Church's music and song, is written what Gerhard would later preach from the pulpit for Christmas day:
"The mother of this Lord was a virgin, for thus it was proclaimed in advance in Isaiah 7:14: Look, a virgin is pregnant, and she will bear a Son who will be called Immanuel. God also witnessed this through many a prototype. In Numbers 17:8, it is announced that Aaron's stick greened up and bore almonds; by this is shown that Mary, foreign to every natural and fleshly bloodline, force, or power, as a natural mother yet bore a true Son in a supernatural manner—just as the stick also bore almonds and yet remained a natural stick. Thus, in Judges 6:38, 39 God performs a sign before Gideon so that the dew fell on the spread-out fleece, but the entire ground remained dry; the next morning the fleece remained dry, and the ground was wet. Thus the pure virgin Mary alone among all women, through the working of the Holy Spirit, received this heavenly Christ-dew, about which Isaiah 45:8 states: Drip down you heavens from above. Later, this dew came upon the entire earth, that is, the fruits of this birth pertain to all mankind; however, Mary once more became a dry pelt, that is, she remained a pure virgin after the birth, just as she was before the birth." (Postilla I:51)
The sequence also likens Mary to the burning bush, and this we also find in the self-same homily of Gerhard: "By this fiery bush is also indicated that the Son of God wanted to assume His human nature from a pure virgin, without violating her virginity. For, even though the virgin body of Mary became pregnant by being filled with the Holy Spirit and by the overshadowing of the highest, yet her virginal chastity was not damaged." (Postilla I:46).
The original sequence included an invocation of the virgin (side-ways, at least), asking Jesus to "save us who pray to your Virgin Mother." This, of course, was altered to bring it in line with the Lutheran conviction that all invocation is addressed only to the Blessed Trinity: "Save us, Jesus, who pray to your Father."
What I think all this shows beyond doubt is that the Church teaches us in the liturgy how the Scriptures are all Christ's book and thus are filled with "prototypes," intimations, if you will, of the incarnation, crucifixion, return and reign of Christ. Fascinating, no?
