In the fifth stanza of the hymn "Ad regias Agni dapes," the word cui is set to a single note. Should it be pronounced like qui? Does this change the meaning?
Yes, it's pronounced the same; it doesn't change the meaning. But going by the online Lewis & Short dictionary, http://www.perseus.tufts.edu/hopper/morph?l=cui&la=la#lexicon it seems that "cui" is only written in place of "qui" in certain uses.
In most cases, "qui" and "cui" are treated as one syllable, but on Palm Sunday, in the hymn Gloria, laus, et honor, "cui" is two syllables.
To participate in the discussions on Catholic church music, sign in or register as a forum member, The forum is a project of the Church Music Association of America.