What categorizes a soundtrack as a particular genre?
I was thinking about it this morning.. given an exact same collection of classical instruments (strings, winds, brass, percussion) and nothing else, what is it that makes you think "hmm, sci-fi" when you hear a piece. Or when you hear it, you think "fantasy... swords & sorcerers," or something along those lines. And I'm not talking about evoking moods like mysteriousness, suspense, romance, etc., because obviously you can have those types of moods in fantasy (LOTR), sci-fi (Star Wars, Star Trek, etc), and other types of films. But for example, if you hear a majestic main theme for a movie, what distinguishes it as fantasy or sci-fi? Or is there no such distinction with some films? Thinking of the LOTR intro theme (e.g. "Foundations of Stone" from the first soundtrack), I suppose it doesn't sound too genre-biased.. maybe a little towards the fantasy side of things. But some parts (LOTR - Two Towers, "Breath of Life", at about 4:15) sound decidedly fantasy to me.
So what do you think it is? The use of certain intervals? A certain combination of instruments? (horns seem to be heavily used in fantasy stuff, but not exclusively so) Discuss.
EDIT: I take back what I said about Foundations of Stone.. it starts off pretty genre-unbiased.. but once you get into the part with the choirs & heavy drums.. it sounds pretty fantasy to me.
Re: What categorizes a soundtrack as a particular genre?
This is the topic of many dissertations and subsequent books. The long and short of it may be that we develop expectations through repeated associative experience. These are not absolute, but through enculturation we develop similar associations. Music can be a difficult topic to study psycological associative similarities as most people lack the vocabulary to describe the music in anything more than a general manner. To the general non-musically inclined population sci-fi music and fantasy music may not be as readily distinguishable as it is to you. There are also studies that show music association differs greatly between the sexes of the same culture. These examples relate to moods, but I believe they illustrate my point on experiential association.
Take "Jaws" for example. The 2 note leitmotiv sets up a general expectation based on all the things you mentioned (interval, range, instrumentation, rhythm, etc.) That is "something bad is going to happen." Until this happens once on screen we are not exactly what this scenario signifies specifically, but our experience tells us it won't be good. After this culminates into a shark attack we associate the leitmotiv specifically with "shark attack."
To further the expectations argument we can look at ethnic inferences. The music can reinforce an exotic geographic location, say China. The composer may choose fourths and several gongs. The music itself rarely, if ever, is ethnomusically pure. Certain key borrowed elements can tip our perspective because culturally we associate these combined elements with Chinese culture.
To believe we make these associations on absolute musical elements is to deny the overall impact films provide to our collective consciousness. The perception of an interval changes based on its harmonization and range. There is a relatively limited orchestration pallete used in Hollywood overall as well. Yet these things contribute to invoke our experiential associations, but it extends beyond purely absolute musical elements. Also, don't deny how the impact the overall film experience has colored your perception of the score soundtrack. It may be interesting to try to identify several scores that you are unfamiliar with blindly and see how close you can guess the genres.
To continue to explore this theory check out some books that discuss this in detail. These may include:
"Hearing Film" Anahid Kassabian
"Overtones and Undertones" Royal S. Brown
"Film Theory Goes to the Movies" Henry Giroux
"Unheard Melodies: Narrative Film Music" Claudia Gorbman
"Music Alone: Philisophical Reflections on the Purely Musical Experience" Peter Kivy
"The Technique of Film Music" Manvell & Huntley