Why should anyone study the psychology of music? And if one decides to study it, who should one ask? A musician, or a psychologist? Or someone else?
There is some agreement (Davies 1978, Sloboda 1985) that there is a problem in the study of the psychology of music. The problem exists for a number of reasons, but the fundamental reason is the difference in approach to the subject of music by psychologists and musicians. There are quite clear, obvious and fundamental differences in training between psychologists and musicians; the likelihood is that the psychologist will simply have an interest in music, and vice versa. Psychologists will in general what to be able to perform rigorously controlled and measured experiments - the musician will often follow intuition (even if they think they're being rigorous!) and, moreover, musicians tend to be more interested in the entire musical activity - complex, multi-level and mixed up as it is, rather than the minutiae of appreciation of note groupings.
These two areas are not the only ones where these and other similar problems have emerged. Here is a comment from the archeologist Steven Mithen:
...why ask an archeologist about the human mind? People are intrigued by various aspects of the mind. What is intelligence? What is consciousness? How can the human mind create art, undertake science and believe in religious ideologies when not a trace of these are found in the chimpanzee, our closest living relative? Again one might wonder: how can archaeologists with their ancient artifacts help answer such questions?
Rather than approach an archaeologist, one is likely to turn to a psychologist... Or perhaps one should try a philosopher...Perhaps a neurologist...perhaps a primatologist...artists, athletes and actors - those who use their minds for particularly impressive feats of concentration and imagination. Of course the sensible answer is that we should ask all of these: almost all disciplines can contribute towards an understanding of the human mind.
Steven Mithen, Prehistory of the Mind, p9-10
And here is another from the evolutionary psychologist Daniel Dennett:
There is no such thing as a sound Argument from Authority, but authorities can be persuasive, sometimes rightly and sometimes wrongly. I try to sort this all out, and I myself do not understand all the science that is relevant to the theories I discuss, but, then, neither do the scientists (with perhaps a few polymath exceptions). Interdisciplinary work has its risks.
Dennett, Darwin's Dangerous Idea, Preface.