AFIK (and experienced in my University years) in a library the taxonomy is fundamental to allow scholars' researches, so if the subject of a research is "maritime trade in XIX century" you may consult all texts, mainly historical, but even novels, think about Joseph Conrad, that might be interesting, IF some smart librarian added "seafaring tale" in the subject of the book. An accurate taxonomy is essential. That's the reason because filing is a study subject. Basically taxonomy is a map for scholars and it should be updated according to new subjects and discoveries.
edit: since I don't have such a huge musical library and I am the one and only scholar of it, I simply filed the records in alphabetical order.