Sound Effects and Music.

Sound Effects and Music.
Sound effects and music within film is a very important aspect, music can help build the tension of a scene and sound effects can be used to make subtle things such as a door creaking open or the dripping of water more apparent to the audience. The most renowned scene for use of music and sound fx would most likely be the shower scene from Alfred Hitchcock's 'Psycho' as displayed below

As you can see in this scene music is implemented to create shock and horror to the audience and sound fx has been used to make the lesser obvious sounds more noticeable such as the shower curtain's rings snapping and the running shower.
Sound effects themselves are used mainly for diegetic sounds whilst music is implemented usually for non-diegetic sounds.
Obtaining music and sound effects is a relatively easy task you simply have to go on a website which has downloadable music and fx register and download. www.filmsound.org has a comprehensive library of websites containing free music and sound effects.