tropus

Carolingian times and later: sequence, tropus, poly - phony, all regarded as particularly closely related to the angelic song.

MUSIC AS A DIVINE ART REINHOLD HAMMERSTEIN 1968

In reasoning thus, one would have to presuppose that over one syllable of a liturgical text, e.g. over the e of the Kyrie, a longer melisma was sung, which bore the name of tropus; furthermore, that to such a melisma a text was composed later on, and that this text was also called "Tropus".

The Catholic Encyclopedia, Volume 15: Tournely-Zwirner 1840-1916 1913

Trope [trōp] noun From the Latin tropus, from Greek tropos turn, way, manner, style, trope, from trepein to turn

p3 - Persuasion, Perseverance, and Patience 2008