The relationship between the visuals and the music is about how the video is cut/changes with to the beat. There are three types of ways that music videos work to promote their song.
1. Illustrative - when a music video uses pictures/images to illustrate the lyrics and the genre of the music video. An example of this would be the music video 'Fancy' by Iggy Azalea. In this music video there are a lot of visuals to the music, which is upbeat and even the video has cutting to the beats and fast editing.
2. Amplify - when a music video repeats effects and/or meanings of the lyrics to the audience. With the music video 'Can't Stop The Feeling' by Justin Timberlake, the beat and the visuals are built up and the meaning is repeated over and over again with the artist dancing to the beat as well.
3. Disjuncture/contradicting - when the meaning of the song is ignored and the visuals are more important. An example of this would be 'Bad Romance' by Lady Gaga, which has Lady Gaga dancing around and being provocative but having nothing about romance.