Harmony in film music is a sprawling topic with many diverse influences. This is because harmonic language is a component of musical genre and style, like instrumentation, rhythmic vocabulary, and melodic form. Film music isn’t a style so much as it is a context. The music is reflective of the style, spirit, and culture of the film itself. Perhaps all musical styles have been imported into film music at some point across film history. Let’s say, there’s a film that takes place in Dublin, Ireland in the 19th century. Irish fiddle music might be a major style influence in the score. Were the movies set in the same place 1000 years earlier when the city was a Viking outpost, Nordic music might be the style influence. So the basic harmonic vocabulary of a film’s score will often be informed by the music of the time, place, and culture of the film. However, since harmony is a deeply expressive, flexible, nuanced dimension of music especially of mood intention, film composers will bend, tweak, and modify the harmonic vocabulary of the style to serve the films needs. Perhaps there’s a Ghost Fiddler in that 19th century Dublin film, the fiddle music might be made bizarre and dreadful through harmonic choices that would never occur normally. But the composer must be careful not to use what might seem like the wrong harmonic vocabulary and accidentally transport us to the wrong culture. Perhaps the composer would write rich tense chords underneath the film, but avoid making jazz or layer multiple lines of fiddle but not write a Baroque fugue. The art becomes making harmonic choices that seem to spring from the genre influence and from the film and don’t seem like the wrong harmonic vocabulary taking us out of the world of the film.