Diegetic and Non- diegetic sounds

So this clips shows a hard exterior man with all the power in the situation, he puts music on that is in such contrast to the original feel of the clip, originally the audience feel fear and then when the music play the severe juxtaposition makes the audience wonder if the guy with the power who starts dancing is mental or just really weird, why would you play such a light hearted song when torturing another person it seems very bizarre.
The music is a voice over, voice overs are a device used that is not meant to be there it does not really fit in in the world of the film. Other non-diegetic sounds can include sound effects.

Diegetic sounds are sounds that are implied to be there by the characters, it is also called real or actual sound, voices and objects that can be seen are diegetic sounds, they belong in the world of the film.

Sound bridges are a sound that cannot be seen when its made but it has relevance to the scene, an opening of a door which is not seen can be used to show that a new character has entered the scene.