Answer:
a. varying the sizes of the objects to create and illusion of depth
The varying color tones in Paul Klee's "Ancient Sound" were intended to be associated with music.
Paul Klee is an abstract artist whose works are influenced by cubism, surrealism and expressionism. Aside from being an artist, he is also a musician, a violinist. In fact, before painting, he would play violin as his warm-up. This is why the color tones in his artwork express the connection to music.
