As far as I know, there have been several historical decrees of the S.R.C. prohibiting the chanting of the Passion on Palm Sunday and Good Friday by ministers not "saltem in ordine diaconatus constituti".
(These are, to my knowledge, in the official collection of S.R.C. decrees: N. 1588, 16 Ian 1677; N. 2169, 17 Iun 1706; N. 4031, 13 Iun. 1899). The only exception would be the "turbae" which may be sung by a "schola exlaicis conflata" (N. 4044, 7 Iul 1899).
Also, the rubrics of the "Ordo Hebdomadae Sanctae Instauratus" from 1955 explicitly require the ministers chanting the Passion to be at least promoted to the order of deacon.
The basic question of the reader is: are there any allowances in more recent legislation that would apply to the usus antiquior that would allow lay cantors be used in place of clerics for sufficient reason?
