Trope
A textual expansion of a chant.
What it means
A trope is an expansion of an existing liturgical chant. It can be expanded in three ways: through new text underlaid to an existing melisma; through a new melody with new text inserted between the parts of a chant; or through insertions within a passage. Common to all is that a traditional chant is not replaced but expanded and further interpreted.
Musical use
The practice is widespread in the Middle Ages and significant for music history, because new forms emerge from it. From the addition of text to long melismas, the sequence developed as a genre of its own; from dialogically laid-out tropes, scenic forms arose that lead to the beginnings of liturgical drama. Tropes also show how flexible liturgical music was: a traditional stock was not only preserved but continued in writing. In the course of later liturgical reforms, many tropes were abolished again, so that they are tangible above all in manuscripts. Tropes arose from the ninth century onward in monasteries such as St. Gall and Saint-Martial.
Performance practice
In performance it must first be clarified which part is the base chant and which is the trope; this distinction should become audible, for instance through alternating scoring of soloist and group. Shape the untexted and the texted sections in their own character, not uniformly. Keep tone production and tempo consistent, so that the expansion remains recognizable as part of the same chant. Check the edition used, because tropes survive in different versions and editors take different approaches.
Bear in mind that tropes survive in different versions and editors take different approaches: check the edition used and clarify which part belongs to the transmitted base chant and which was added. Well known is the Quem quaeritis trope to the Easter Introit, a starting point of liturgical drama.
Check whether a manuscript transmits the trope in full, because additions by editors are common and should be marked as such.
Also check whether the base chant is printed in full in your edition, because it forms the frame.