The use of music as an exercise for poorly moving joints and weakened muscles is recent and may be said to have received its great impetus in the Second World War (described in the Boston Sunday Post, February 11, 1945; A-5). _CHAPTER TWO_ PHILOSOPHY AND PSYCHOLOGY OF MUSIC I In the realm of thought, opinions and theories sometimes find credence long after they have been proved incorrect. In the field of the arts, opinions may become so strongly rooted that there is occasional resistance to any analytical attempts designed to disprove them, and even after they have been exposed, there will be a significant number of people who will continue to believe in them. The artist who would make music for patients must approach such an endeavor with a full knowledge of the elements involved, and should be willing to recognize those prejudices, customs and thoughts concerning the effects of music on the human body which have been fostered by well-meaning, but misguided, enthusiasts. We must differentiate between the philosophy of esthetics and the proved psychology of music. Musicians who refuse to accept those results of scientific research which disagree with their personal views will fall into the same difficulties which have beset so many musicians in the past who have desired to help patients. Before the advent of laboratory psychology, there was no satisfactory test for the theories which dealt with music and the mind, and the number and variety of theories advanced were great. Some of the most unreasonable were the most attractive, and it is easy to understand why they were accepted. But if any of these theories is used as a means of attaining a scientific end it cannot succeed with any dependability if it is unsound. The psychologic effects of sound may be physiologic or intellectual. They may be related to intensity, quality or direction on the one hand, or to past or present mental associations on the other. To the primitive man thunder, which seems to come from everywhere and is louder than anything he can produce, is terrifying and supernatural; the rustling of leaves is frequently caused by the wind, but from his past experience may also instil the fear of the approaching enemy. Sound is often frightening from its qualities or implications. The psychologic reaction to the type of sound known as music may vary from the reflex panic produced by the air-raid siren to the soothing effect of a softly sung lullaby. For some people, certain musical selections elicit almost no response, while in still others a truly amazing chain of mental images results. The latter reaction is the result of centuries of evolution in the development of music and knowledge, and will be discussed later.