We save the music categories to the end to analyze for two reasons. One is that it helps to have heard the music. While it obviously helps to have seen any contender before opining on its chances, I find that listening to the music is one that really cannot be compromised. It is easier to guess what the costumes or cinematography of a movie might be like. It's also nice to have the list of qualifying scores at the ready.
The second reason is that composers themselves are usually brought on to the films quite late. After the actors, writers, cinematographer, production designer and costume designer have all gone home, the composer is left by him or herself, watching a movie he or she had no part of shooting.
Bernard Herrmann‘s brief appearance in “Hitchcock” was, alongside the ending, my favorite scene in the movie. It also showed two very important aspects of film composing. First, it showed how composing is lonely, painstaking work with no one to keep you company save for the occasional appearance by the producer, editor, sound mixer or, most likely, the director. But second, when done well, film music can become iconic. From “Star Wars” to “Lawrence of Arabia” to “Gone with the Wind” to, yes, “Psycho,” many themes are simply unforgettable. They can also create mood and atmosphere.