Which voice parts are singing this music?

Mondrian's Composition with Blue and Yellow is

A. a photograph of dancers in Times Square. B. an example of the de Stijl movement. C. a neorealist representation of dancers in action. D. a surrealist design charged with erotic elements.

An abrupt change from soft to loud or loud to soft is known as ________.

Fill in the blank(s) with the appropriate word(s).