From 《The Music of Man》 (8)

For music to speak to us, it needs more than the structure of a scale, of intervals, or even of our emotions. It needs a recognizable form corresponding to something in our own being. I have often thought that the earliest musical form must have been a simple repetition, a double image rather like the right and left halves of a leaf when folded upon each other. We recognize the repetition of two roughly equal halves in a rhythm or melody, and this gives us a sense of security and completion, and with that musical memory we begin to build. Once we hear a sound we can repeat it, creating a simple rhythm at first. When we put a few sounds together in groups or phrases of related tones, we have the beginnings of melody, a blend of feeling with logic. We can also turn these phrases or rhythms upside down or backwards, for one of the basic tools of conceptual thinking is to consider a situation in its reverse.