If you were looking for something about the speeches in a particular Greek tragedy, the best that the Library of Congress offers by way of subject heading is, well, nothing. If the work is about some feature in the Alcestis, for example, then all they do is provide a subject entry for "Euripides. Alcestis". Here's an example of inadequate (or feckless) subject analysis: Victor Bers's Speech in speech : studies in incorporated Oratio recta in Attic drama and oratory contains some interesting consideration of direct quotation in Greek tragedy. The Library of Congress can only approximate the topic with "Speech in literature". (The other headings in their record refer to actual oratory and ancient rhetoric). So you can only hope that the title of the work has the word "speeches" in it.

In general, it seems as if cataloguing agencies haven't spent a lot of time classifying the humanities. The banausic, on the other hand, is dealt with in compulsive detail. That seems inappropriate, because scientists and engineers don't know how to read.