Should a composer write a film score to a horror movie, one might reasonably expect that the harmony would include a great deal of:

Dissonance

Explanation: Dissonance is a mixture of disharmonious sounds used mainly to create a harsh scene especially in horror movies. Dissonance can also be described as disharmony between Musical sounds,it is the opposite of Assonance. Horror movies which are movies containing very harsh and unpleasant scenes,will most likely contain a lot of Dissonance which will help to portray the harsh situations the film director wants to show.

answercouplet;

the style of music that was composed during the classical era was concerto grosso.