The Imagination and the Unknown
Far more frightening than what can be visually represented on a screen is the images that our own imagination can produce. This is why often the most successful examples in the horror genre delay or deny the audience the chance to see the fear being embodied. A fear of the dark, for instance, is the fear of the unknown, it is a fear of those things that we imagine can inhabit the dark. The player should know the nature of the threat but not the specifics.
In the Silent Hill series, the fog that envelops the town serves as the perfect way of obscuring the player's view and keeping the player 'in the dark' as to what they are about to encounter. However, since the games lack a musical score through large sections of the game (particularly those where fog is used), the anticipation of an encounter with some kind of monster is created by a broken radio that crackles as monsters come close.
Example of the use of fog from "Silent Hill 2".
In this way, we have the anticipation of an unknown threat; one which the player cannot prejudge and rationalise in order to make safe or comfortable.
Feelings of Helplessness
The most frightening visuals and musical score will only go so far unless the player has a feeling of absolute helplessness. There must always be the risk of negative consequences - of getting hurt - otherwise the threat that the fear should embody can never be fully realised. In many survival horror games, a feeling of helplessness is created by a method that could be known as "Resource shorting" - denying the player the resources to be able to dominate their surroundings; weapons should be able to break or run out of ammo, or be limited in how useable they are in certain situations. The player should be made to want to avoid confrontations altogether rather than seek out and destroy enemies.
An example I would like to use here, but which may need some explaining, is that of Dead Rising. I would argue that the beginning of this game is actually rather frightening. You come across a group of survivors penned up in a section of a shopping mall against a zombie outbreak. When the zombies break in, the only course of action the game lets you take is to escape. Meanwhile, other survivors are being killed all around you. Although the game simply doesn't let you save them, at this point, having just started the game, you're level 1 (out of 50) and inexperienced with the controls - even if you attempted to save them and the game let you, the chances are that you would fail. The whole scene serves to make you feel utterly helpless against the oncoming zombie assault. However, as the game proper begins, and you gain access to more and more lethal weapons, this sense of fear gradually subsides. Once you acquire guns and chainsaws, you can begin to feel rather relaxed about the whole affair.
Another case in point, though rather different, of this type / method of fear comes again from Silent Hill 2. The opening sequence appears, on paper, incredibly drab and boring; it consists of you walking James across a very lengthy path in the fog, encountering no enemies and where nothing happens. Yet, once you add an unnerving musical score (frequent bestial and mechanical noises) and actually experience it, something rather innovative happens. The physical length of the sequence contributes precisely to a psychological separation from the real world, to a sense of loneliness and the inability to turn back.
The Sound of Fear
The music of the horror genre has been considered often more frightening than the visual aspects. Part of the reason behind this must be the ambiguity and the aforementioned power of the imagination in creating fear; create the sound of something creepy, but whose identity or source isn't yet known, and you leave the rest to the player's imagination. What you also do is set up the anticipation for an encounter...
John Williams' score to the film Jaws is a great example of the way in which sound can come to be associated with a threat. The arrival of the Great White Shark is precipitated by the start of the music (see link below to remind yourself how
Sound sample from the song "Jaws Theme" by John Williams.
This raises a significant point: the "music" of the horror genre is as much about the absense of sound as its inclusion - to have a climax there must be an anti-climax, tension cannot and should not be sustained indefinitely. Music and sounds are only effective when they are contrasted by periods of silence or minimal sounds. The repetition of footsteps on a surface, with nothing else playing, is one example. Music should be introduced when the player enters a new situation or locale, is about to stumble upon something, or to coincide with the discovery of something visual.
In the Irrational Behaviour podcast found in "Sources", someone talks about the creation of sounds from the familiar and everyday. This is an interesting point; if you can place something which people can relate to (e.g. furniture) in an unfamiliar setting or circumstance (covered in blood or in the middle of a corridor) then you will unnerve the player a lot more than by utilising something that is rarely seen. The same applies musically. The example in that podcast is of the sound of an un-oiled oven door being opened, a sound we may have encountered before; the sound could be amplified or distorted, or transplanted to somewhere unsettling - it becomes more frightening for being vaguely identifiable.
Friedman, Lester D. (2006). Citizen Spielberg. Champaign: University of Illinois Press.
Irrational Behaviour Episode 5 (podcast): http://irrationalgam...vior-episode-5/
Kirkland, Ewan. "Restless Dreams in Silent Hill: Approaches to Videogame Analysis". Buckinghamshire Chilterns University, 2005. http://www.meccsa.or...05-Kirkland.pdf
Music in the Horror Film: Listening to Fear. Ed. Neil Lerner. New York: Routledge, 2010.