Subject specialist librarians are eager to assist you with your library research, and in most cases can save you a lot of time, especially if you meet with them early in order to plan out your research strategy.
Subject specialist librarians recognize the interdisciplinary, collaborative nature of historical research, and they encourage you to meet with any librarian whose area of expertise overlaps with your research. For example, if you are researching the history of house music, then you should meet with both the History Librarian AND the Music Librarian.