DISCLAIMER: Usually I do research before I write. But the factual basis on this topic are pretty... meh.. So this time it was the other way around. So take note that the arguments here are just ideas. If you find references to empirical studies that support/deny these claims please leave a comment!
Turns out that I wrote a whole frickin' article in a short time. But I think this topic deserves it.
Short Answer:
- Music is a primitive form of language. Both are sound patterns meant to convey information. Humans are drawn to music just as they are drawn to language.
- When compared to visuals, noises are harder to localize and can't be back-checked. It's essential for survival to get the most information out of very little sound. That maybe explains why humans are so easily fascinated/obsessed with even slightest details in melodies and rhythms.
- Mothers share their emotional state with their baby via endorphins, stress hormones etc., and that baby may associate these emotions with her heartbeat in the womb, learning a sense of rhythm.
Long Answer:
What came First? Talking or Singing?
What is singing? Singing is like talking, but with a melody. And when singing, we don't really care that much what words are used. That makes singing an easy way of conveying emotions between each other, much like a "primitive" form of language. Look at the asian language: Words shift their meaning when changing pitch.
So I had this idea that our complex language must have evolved after we began to sing. And it turns out that I am not the first (this article).
Even Charles Darwin "talked about our ancestors singing love songs to each other before we could speak articulate language," Patel says.
I think this makes it clear that our love for music is deeply rooted in our love for language.
This article also claims music is deeply rooted in evolution:
Music making seems to occur, in some form or another, in all human societies. Although musical behaviour varies in sophistication, music itself seems to be universal across all human cultures and plays a key part in rituals of all varieties, and the origins of these practices seem very ancient.
Detecting Sound-Patterns Is Like Learning a Language
Human hearing however, is unique among to animals. We have evolved to learn and speak a ridiculously complex language. And toddlers do not seem to have any issues by learning that language all by themselves. When mommy's lips move, sounds come out. And at some point they recognize a patterns of speeds, noises, repetitions, etc. They all represent and define things that we see around us. And learning these definitions is fun, because it helps them getting exactly that thing that they want right now.
My point is: Music is basically noises arranged in a complex pattern. But other than language, these patterns have no specific meaning. Still, that does not stop our inner child from trying to learn those patterns. After all, those patterns might tell us something.
Small Sounds Must Elicit Big Emotions
Hearing is essential to survival. Hearing must elicit an emotional response in the right situation in order to regulate our behavior. A hissing sound in a bush means "don't stick your hand in there". Screaming means problems. Yawning means sleep. Whispers mean secrets. Laughing means happiness.
But the problem with sound is, sounds can not be perceived a second time if we want it. If we see eyes looking at us from between the trees, reality allows us to look again and check. Noises however are harder to localize, so they are often singular events. And they can easily be missed or ignored. And that can have dramatic consequences. That’s why I think that the control of hearing over our emotional state must be so strong, so that even small sounds are allowed to override our current emotional state. It’s essential to survival, being able to instantly switch from e.g. relaxing at the campfire to standing up and checking in on the sound of branches breaking.
And I think that this idea goes even deeper. It’s not just branches breaking that should freak us out, but all those sounds that humans make. After all, the only dangerous „predator“ left to humans are humans. And humans can be hard to read. What did he say? How did he say it? Is he lying..? Did I say something wrong? Does he/she love me? And to read a human successfully, we must be able to discern even the slightest shifts of volume, pitch, tone, speed, etc.
My point is: We love hearing details, since it has always helped us to survive. And Music is full of details that are just waiting to be over-interpreted.
An Unborn Child may Associate Heartbeats with Emotions
But how do we learn to enjoy music in the way that we do? Why do minor chords sound sad, and major chords happy? I don't know the answer, but I might explain why we are able to associate different rhythms with emotions.
The first sound we ever hear is the heartbeat of our mother. It can be fast or slow. And that has a meaning. When mommy's heart is beating fast, she's also getting warmer. Also, the levels of hormones (Stress hormones, endorphins) in her blood change. In other words: A mother shares her emotional state with her baby. In fact, a mother's stress can change fetal heartrate, too (Monk et al. 2000).
And I presume that the child is able to associate different heartbeat frequencies to stress/happyness in the womb already. That might be the reason why we perceive slow rhythms are calming and faster rhythms as exciting.