Which artistic element of theatre would be the most challenging?

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.

Which of these forms or genres appeared in the baroque period, but  not  previous periods?

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