Why are constrast and chiaroscuro an Important part of realistic painting?

Why is macbeth fearless in the final battle

Afilm, like any other artwork, can never be totally understood and appreciated through critical analysis, no matter how complete or astute, although such analysis can open up new levels of meaning and appreciation for the sensitive viewer.

I’m a paragraph of no less than 125 words, explain the single most important factor involved in advancing american classical music in the twentieth century.