Music can certainly affect people. There is no question of that, as it can be either enlightening or entertaining or any number of other things. This observation leads naturally to looking for direct physical responses to music, and of course there are some things which can be said in that direction. Sound makes the ears vibrate and stimulates the nerves, and so we might think that a better understanding of the brain will allow us to circumscribe musical experience. Taken in isolation, some sounds are pleasant, some are unpleasant, and others evoke little reaction or maybe an orthogonal reaction. For instance, the sound of someone speaking can be pleasant or unpleasant, but more often it is divorced from these qualities in our apprehension. When it comes to music, it is frequently suggested that there are real constraints on human appreciation which can make an approach to music-making falsifiable. At some level, this is certainly true. We could generate sound waves which are outside the limits of human perception, or even make something so loud that it literally destroys its audience. Of course, those are easy observations, but there is also the contention that even some of the "music" which is played and supposedly enjoyed is not physically suitable to the human form.
One reader, Brian Fisher, raises a good example. He suggests that much youth-oriented popular music is intended primarily to invoke a visceral or hormonal response. I might go on to suggest that we can still enjoy the popular songs we enjoyed in our youth because we remember the response they invoked, even if they do not invoke it now. I continue to observe the response, which suggests that memory can allow the actual stimulation to be reproduced. I say "memory" because today's popular music induces no such response. So the first larger point is that, even at the most visceral level, our age mediated by our memories conditions our response. My heart rate does not increase for today's teenage music, because I feel no connection. Another good example is the often-quoted results on listening to Mozart correlated with IQ scores. Even if we accept the results, and I do not find them so hard to believe, many of the larger implications remain dubious. First of all, I submit that "IQ" and related tests are simpleminded. In turn, Mozart establishes clear expectations drawn from a small finite set with the result repeated again & again in a slightly varied context. To me, this is the essence of the standardized multiple choice test, but certainly not of life as a whole. The second larger point, one mentioned earlier, is that music is well-suited to illustrating patterns of thought, provided one can connect with it to apprehend them.
Apprehension is the key to this entire discussion. Statements about the soothing or agitating quality of specific music frequently break down across cultures, precisely because lack of comprehension is inherently agitating. This brings us back to complexity, and what can actually be apprehended. A simple observation, worth repeating, is that what can be apprehended with more exposure and education is substantially more than what can be apprehended otherwise. For many types of music, this exposure is widespread from birth, which is why cross-cultural comparisons can expose some flaws in arguments about what makes a melody inherently more natural. The situation for harmony is more complicated. There is no question that simpler integer ratios yield combination sounds which are more easily apprehended. But how difficult is too difficult? It is clear that there is no universal answer to this question. What preparation does one have already? How much is one willing to invest in developing an understanding? No one can answer these questions in the same way. At some level, all tones are related, to the point where we can derive relationships which may not be intended (the latter is a big cross-cultural issue too). How far afield can we go to make these relationships? Very far indeed, but that does not mean everyone wants to follow! If one is bombarded with something one cannot understand, the first response is agitation, but if it continues relentlessly, the result is malaise and then perhaps defiance. (This also describes the American social landscape as a whole.) Presumably, it is not a desirable effect on an audience. However, the reverse situation is never to be challenged, and that equates to death. Each person wants the correct degree of challenge, and that is the third larger point. It is physical reality, observed in something as simple as weight training.
Some people will insist that certain music is impossible to apprehend, although that is typically false. They are free to set their own priorities, and not be begrudged for them, but implying e.g. that anyone who enjoys Webern is a liar is pure vanity and bad manners. Another school of thought, perhaps more insidious, is that if everyone were the same, the issue of differing apprehension would vanish. This is not so unlike Mozart's audience in Vienna, and clearly such an environment can serve to nourish art, but it is not something one simply decides, at least not without severe consequences. There is still the physical reality that with such a wide range of nearly continuous stimulus in our modern world, there are limits to the interests one can pursue. It is true that there are only so many hours in the day, and even if the rate of human apprehension does vary substantially, it never becomes close to infinite. If we deny the multiplicity of artistic endeavors and insist that music must be "uplifting," we still cannot escape this bind, since what is uplifting to one person may be trite to another or incomprehensible to yet a third. We can observe the brain stimulus, but we are hard-pressed to observe ourselves making meaning of it. While there is some contention that physiopsychology will conquer this threshold, art by its nature easily jumps to the next and then the next. As always, it is art reacting to theories which prevents theories from prescribing art.
Finally, to look at the other side of this equation, the audience will identify with the musical performer, and that includes physically. This is clear in the case of hero worship, and goes some way toward explaining the appeal of virtuosity. So I will suggest that while people may wish to see the performer do something superhuman, they do not wish it to be inhuman. In other words, there are strange contortions which might make us cringe, simply because they are unphysical to perform. Rather than requiring ordinary dexterity to be extended in its usual parameters, whether in speed or range, they might require strange leaps back & forth or awkward starts & stops. This may be exactly the "failing" of dodecaphony, as the lines are so very difficult to sing, not in the sense of requiring more range or more breath support, but in the sequence of notes which requires the singing apparatus to move in a different way. The pure physical majesty of the act of performance is the sort of relationship people internalize, more so than any rules of tonality. This is a big reason to retain a dedication to human-performed music. To have full communication with an audience, it is important to have that kinesthetic association. If we are to talk about "brain development," it is simply impossible for passivity to produce the same mental image as the direct knowledge that another person is actually producing the sounds. As it becomes fashionable to talk about types of intelligence, let us remember to embrace the kinesthetic as well.