“A mood music sounds makes the scenes slowly so that some unusual events will be waiting”, this is a great analysis of the Non-diegetic sounds, which is also wildly used in horror films. The background music is one of the example. In Buffy, the director use music many times, it usually combine with lights effects and the whole atmosphere would change, this also promoting the plot development and catch people’s mood. On the other hand, the diegetic sounds are more like to occur to suits the need of story. they are actor’s actings, the sounds that come from the screen space. These are the differences between these two sounds, one is for add effects, and another one is for create the story and lead audience to the plot of the film. after apply these sounds in a horror film, the atmosphere has already create and catcher people’s curiosity. At this point, camera just follow actors’ move and show the perfect horror scenes.