PDF • “Rorate Mass Musical Booklet” (39 pages)
In my humble opinion, that ‘explanation’ is sheer, unadulterated gobbledygook.
Pope Saint Paul VI (3 April 1969): “Although the text of the Roman Gradual—at least that which concerns the singing—has not been changed, the Entrance antiphons and Communions antiphons have been revised for Masses without singing.”