There's an interesting musical phenomenon in "O Virgo Splendens" (14th century, in the Llibre Vermell de Montserrat) as it is consistently interpreted across all editions I have ever encountered.
The piece (a round of three) consists of 12 musical phrases of identical length and rhythm: 15 eighth notes (5 triplets) followed by a dotted quarter or in the interpretation I prefer, a dotted half -- in any event, an on-beat cadential note. There is no rhythmic variation in the pitches of the phrases. All of them have the exact same rhythm, and it's the simplest possible rhythm: a series of 15 notes of identical length, then a held note on the end.
The text, however, is assigned to the notes in ways which syncopate them. For instance, the 7th phrase starts with the word "conscendunt", each of the three syllables of which gets two eighths, turning those two triplets into a frank 3/4 hemiola. Examples of this sort of syncopated text underlay abound throughout the piece.
As a consequence, the piece is actually much more rhythmically challenging to sing, even just as a solo, than "15 eighths in a row, all starting on a downbeat" would ever suggest. Sung as a round, it becomes quite rhythmically complex and texturally rich, to the point of being challenging to sync the lines properly -- even though, technically, rhythmically, all the notes are strictly homophonic!
Is there a technical term for this? For syncopation that exists entirely in the syllabic assignment of a text in a vocal work and is otherwise not represented in the durations or marked dynamics of the notes?
And are there other examples?[*] Either contemporaneous or otherwise?
[* The only other thing I can think of is a brief moment in the 16th cen instrumental pavan version of "Mille Regretz", third system "...brief mes jours definer", where if you don't know how the text goes in the original Josquin chanson, you will misconstrue the phrases. But that's not even really syncopated.]