Hi Andrew, I'm really delighted at the work you've undertaken with Manchicourt!
CPDL editors have resorted to (Nth setting) before, both with a Roman numeral Gaude visceribus II (Anonymous) and occasionally in English In manus tuas (1st setting) (John Sheppard). These are unambiguous because they were copied successively in a unique source (though it's a little confusing there's a Gaude visceribus (Anonymous) but no Gaude visceribus I (Anonymous)). I once preferred Parce mihi Domine (1582) (Orlando di Lasso) & Parce mihi (1565) (Orlando di Lasso), his parents having died at the same time and there being no firm chronology for order of composition; I did toy with (imitative) vs. (homophonic) though, thinking it would be easier for others to guess based on a musical description.
All this is a roundabout way of suggesting that it might just be simpler to move Pater peccavi (2nd setting) (Pierre de Manchicourt) to Pater peccavi a 4 (Pierre de Manchicourt), with Pater peccavi a 5 (Pierre de Manchicourt) the only other setting. ;-) Richard Mix (talk) 04:10, 5 October 2019 (UTC)