The Appeal of Music

Why is it that hearing only up to the seventh of the eight note octave leaves us with an unsatisfactory, discomforting feeling? I remember as a child hearing my piano teacher tell me the story of how Mozart's mother would play C up to B on the piano in the morning, because it forced Mozart to jump out of bed and run to the piano to play that final C. There is something special, even self-completing to the sound of hearing the whole scale to any musician. But why is it that this particular set of frequencies is so "nice" to us? As Dr. Gary Marcus asked us at the Loyola University Neuroscience Banquet last Saturday, what might an alien find pleasing, if they liked music at all? A 61 note octave, or perhaps 27? An even better question, why are so few mammals on Earth able to appreciate music? Very few have been identified as having care for music being played.
Dr. Marcus argued that music has evolved due to a kind of sexual selection among humans. Those of us who could, for example, sing best may have attracted the most mates. And those who lacked the capacity were more often excluded. But, he also brought up, there are many examples of relatively smart and extremely productive people who have had no care for music, such the infamous psychologist Dr. Freud. In addition, there is absolutely no evidence that has shown that musicians are better able to find mates in this day and age. However, it has been incredibly difficult for musicians to maintain a steady career or even become well-known until the dawn of record players and the radio. In the Medieval Ages musicians were seen as a "lesser" career, to be looked down upon.
Music as we know it now has really only become the "way it is" within the past millennium, an insignificant period of time compared to evolutionary history. One can only wonder what people preferred to sing, the kinds of beats they made, or how prevalent music was in civilizations at all.
Perhaps music has only become a focal point of our society during these past few hundred years because only now have we truly had the time or ability to produce and listen to it. We enjoy and attach ourselves emotionally to certain songs, whether it be the first song newlyweds danced to or your break up song from high school. Music has a great power in controlling our feelings, but we have little explanation as to why.
Perhaps one reason why like music is the novelty of it, the challenge of predicting what chord might come next or where a song will lead. The reason we don't like random noises nearly as much as we like songs is because it is complete novelty and impossible to predict; i.e., no challenge presented. We like to hear 80% known material with 20% novelty or challenge. We are then able to enjoy the sounds because it is not entirely foreign but it is not so repetitive that we get bored.
Back to the original question, why is it that we like the eight note octave? Well, I haven't the faintest idea, but my guess is that it is just the way our brains are hardwired. Marcus also spoke of his book Kluge, a book about how humans are not the "optimal" organism per se, but we are the optimal solution given what we had to work with from our evolutionary history. I would imagine that we like music in the fashion we do due to mere chance, that as our brains changed over time for important evolutionary advantages, the eight note octave appeal came as a by product. This could explain why dolphins like music in a completely different manner. They evolved differently than we did, and as such their brain formed differently than ours. We started with the same "materials," and we simply went our separate paths.