Diegetic music (The Art of Foley) and sound effects

In the 1920s, Jack Foley became famous for adding sound effects to stories told over the radio. Over time, adding sound effects to the narrative became known as the Art of Foley. You may have also come across the term diegetic sound, which is the same thing. Diegetic sound is any sound that emanates from the story world of the film.

Except for dialog, most of what you hear when you watch a movie wasn't recorded at the time the visual was filmed. Every explosion, footstep, weather sound, movement, animal growl, and other sound effects are sounds that have been carefully designed and chosen after the footage was recorded.

If sound effects are done right, the audience won't notice the film is filled with sounds added in post-production. Excellent sound design matches the visuals with the sound seamlessly, so your mind thinks they were created together.

All sound involves two elements hitting one another in some fashion...