According to Professor Robert Greenberg of the San Francisco Conservatory of Music, the Benedictine monks arranged these antiphons with a definite purpose. If one starts with the last title and takes the first letter of each one – Emmanuel, Rex, Oriens, Clavis, Radix, Adonai, Sapientia – the Latin words ero cras are formed, meaning, “Tomorrow, I will come.” Therefore, the Lord Jesus, whose coming we have prepared for in Advent and whom we have addressed in these seven Messianic titles, now speaks to us, “Tomorrow, I will come.” So the “O Antiphons” not only bring intensity to our Advent preparation, but bring it to a joyful conclusion.
Behold, I am coming soon, bringing my recompense with me, to repay each one for what he has done. (Revelation 22:12)
Even so, come Lord Jesus.