Also known as: underscoring. The opposite of diegetic music. It’s music that’s heard by the viewer but not by the characters. We are able to listen to the music but it’s not part of the fictional setting. So, plainly speaking, if you are listening to music but can’t see anyone holding an instrument or singing during the scene you’re watching, then it’s incidental music. As the main purpose of incidental music is to comment, describe and dramatize what’s happening on the screen, think of it as the person who is commentating a football game.