Music

Music in Horror/Thrillers and usual suspenseful to build the audiences anticipation making the pay off or scary moment more frightening or enjoyable.
 (Opening to se7en)
Some Horror films use uncountable music which makes the audience feel uneasy and the adds more fear. Se7en uses a very uncountable song in it's opening sequence and this added with the unpleasant images that appear make the scene feel more suspenseful.

Other films use music to make scenes more unexpected and scarey by having the music start when something happens and the music will play loudly and sound frantic. In Psycho the music for the shower scene doesn't start until the murder is in the shower and when it dose it's loud and fast and makes the audience jump and makes the kill more terrifying.