Categorizing the listening process
People listen on the sensuous plane for pure entertainment. For example, "turning one the radio while doing something else and absentmindedly bathes in the sound" (1074). Copland continues talking about the "sound stuff" (1075) and how composers manipulate it differently. Good listener should realize that lovely sounding music is not necessarily great music. I believe putting the "sensuous plane" before the other two is a good technique, since this is the plane most people often relates to.
Second plane is the expressive one. Copland now discusses the notion of meaning in music. In his view, music has a meaning but this meaning is not concrete and sometimes it cannot be expressed in words. This plane explains why we get moved or relaxed by music. It is more difficult to grasp and required more deep thought because Copland claims that meaning in music should be no more "than a general concept" (1076). This issue is very philosophical and one must accept the train to understand this plane.
The next plane deals with the manipulation of the notes
Cited: Copland, Aaron "How We Listen," The Norton Reader. Eds. Linda H. Peterson, John C. Brereton, and Joan Hartman. New York: W.W. Norton & Company, 1996. 1175 - 1179