Here is my translation of a German version of "Quod chorus vatum," called "Was uns etwan die heilgen Propheten" (A. Lobwasser, author of the infamous psalter). It is sung to the original melody, which I have seen either as that of "Iste Confessor," or else of "Quem terra pontus ethera" (The God whom earth and sea and sky). This page has more information on the original version as well as an English (unrhymed) translation of it.
WHAT PROPHETS in the Spirit once had spoken
Now we behold fulfilled, the oath unbroken,
By Virgin Mary comes the revelation
Of our salvation.
2. Conceiving Christ, the Son of God, our Savior,
Without a spot or breach of honor ever,
Pure she remained, as even from her mother,—
Such as no other.
3. They took the Child and to the temple brought Him,
To aged Simèon, who long had sought Him.
The priest received the Child with gladness willing,
God's oath fulfilling.
4. And so with fervent hearts, we pray Thee, Savior,
True Son of God, to show Thy grace and favor;
Let us, e'en as Thou art to heav'n ascended,
E'er be defended.
Translation © Matthew Carver, 2012.