Generic titles, those that use standard musical terms like sonata, symphony, concerto, mass, etc.
Distinctive titles, like The Marriage of Figaro, are more unique and do not use generic musical terms.
Unlike the title of a book, the title of a piece of classical music can vary quite a bit. There are often differences in terms of language and/or wording. This can make searching tricky.
For example, W.A. Mozart's String Quartet (K.387) could appear as:
For example, The Marriage of Figaro could appear as:
Music is often located within larger collections (scores or recordings) that are not broken down by title in the catalog. This means that you may have to do a more general search to find what you're looking for.