Hello again- this post is rather short, but it's something interesting that I found. No Musical Find of the Week, sadly- I've been busy with assignments for a libretto-writing workshop, as well as with parents coming to town.
So I was trying to make headway on looking for Hans Schoop's book on text underlay in Oxford 213, and got waylaid by reading a review of a Chansonnier Cordiforme facsimile set. But all roads lead back to Oxford 213, it seems: in a mistaken attempt to find instances of the word 'amour' replaced by a heart symbol or something similar in this manuscript, I found something odd: a partially texted tenor on fol. 91. This usually doesn't happen for most tenor parts in this book: they are either untexted or fully texted in most cases. I would assume that performers are expected to know where they are even without text underlay, so this remains something to chew on for now.
And no, I haven't managed to find an online version of Schoop's book- yet. There are reviews of it, however, some of which are accessible on JSTOR.