The musical scores of John Williams
are best described as neo-romanticism
inspired by Wagnerian music and its concept of
leitmotif (pronounced “LIGHT-mo-teef.”)

A lietmotif (meaning “leading motive”) is a recurring musical theme, associated with a particular person, place, or idea. By extension, the word has also been used to mean any sort of recurring theme, whether in music, literature, or the life of a fictional character or a real person.

Although usually a short melody, it can also be a chord progression or even a simple rhythm. Leitmotifs can help to bind a work together into a coherent whole, and also enable the composer to relate a story without the use of words, or to add an extra level to an already present story.

The word is usually used when talking about dramatic works, especially operas, although leitmotifs are also used in other musical genres, such as instrumental pieces, cinema, and video game music. – Wikipedia