Where did the light go?

This year the Transfiguration falls on Sunday, which allows us to sing the strange, spooky, and mystical Visionem for communion, which lends itself so well to exciting vocal effects. It is also short, which permits the use of verses. In the case of our schola, we sound better with each repeated Antiphon, so by the third time through, this will be spectacular. (You can try this at home by making the first note a D and marching through the white keys with A as the top note.)



Good so far. But when I turn to the Introit, there is an instruction in the Gregorian Missal to sing the Tibi dixit from the 2nd Sunday of Lent. No special Introit for Transfiguration? Can't be. So I open the old Graduale from preconciliar days to find this splendid piece of work, the words of which are: "Thy lightnings enlightened the world: the earth shook and trembled. How lovely are Thy tabernacles, O Lord of hosts! my soul longeth and fainteth for the courts of the Lord."




Look at the range this piece explores just in the first figure, only to have the top note repeated, held and held, followed by a frightening melody, only to have the composition reach even higher, all in the first line, and following back down to the beginning note again precisely where we finish singing about the whole world. Here is the light. And then follows again another outbreak, a stunning scene that reaches again up and follows down again on "terra." Here is a shaken earth.

But where did it go? Why is it not in the new Propers? Anyone know? And what is a schola to do in this case? Is it time for an "alius cantus aptus"?