From the quick research I did on it, the antiphon was written by one Theodore Decker. Unfortunately I have not been able to find SATB of the antiphon myself. The psalm tone used at the National Prayer Vigil for Life is a Dr. Latona original.
Calefrink, I was under the impression that the piece was written by Fr. Noel Darros, organist of Notre Dame. At least, that's who the SSPX hymnal has listed for the composer.
But, as per usual concerning the Society, YMMV! . . .
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