As a rule, humans are very picky about their music. I don't mean stylistic choices. Whether you like country, western, or both is up to you. I'm talking about something more basic than that.
A tone is a sound, like a note before it gets a specific name, and a scale is a collection of tones grouped in ascending or descending order. We are able to hear a huge number of tones and, theoretically, there's billions of ways to group them, but humans tend to focus on a very small number of scales, usually made up of either five or seven tones. The same scales are used over and over, throughout most of Western music and much of human music as a whole, said Dale Purves, Ph.D., professor of neurobiology at Duke University and director of the Duke-NUS Neuroscience Program in Singapore. In fact, even styles of music that sound completely different--say classical Chinese music vs. Western folk music--use the same scale, he said. They just use it differently.
So why are we so drawn to certain tones and certain groups of tones? Purves' team thinks they have an answer--an explanation that links what humans like with who they are, biologically.
The key, Purves said, lies in our evolutionary history.
"Any perceptual quality you have is there for some biological reason. They evolved because they provide useful information to us," he said. "So if you take a microphone out in nature and ask what the tonal sounds are in our environmental niche that we would have evolved to appreciate, the tonal sounds you record are nearly all animal vocalizations. And the ones that count the most are the vocalizations of other humans."The sounds humans make matter most, he said, because that's where we get information about our competitors and our potential mates--the things we need to know to be successful creatures. We developed an ear for the tones common in human vocalizations, the same way a sommelier might develop a taste for fine wines. Those are the tones we find most appealing and thus, the ones we made into our musical art.
The basics of this idea are nothing new. It is, after all, pretty obvious that there's a connection between human voices and human music. But, when people have looked for links between musical scales and the natural changes in the pitch and rhythm of speech, they haven't been able to turn up any solid evidence of a causal relationship. Purves, along with Kamraan Gill, Ph.D., approached this in a different way, looking instead at similarities between scales and the spectrum of--or frequencies in--speech. Here, they hit paydirt. In fact, Purves and Gill found that you can correctly predict which scales are the most popular by how similar they are to the spectrum of human vocalizations. A great example of how this plays out: Rock 'n Roll.
"Rock is especially popular because it emphasizes the musical intervals whose frequency relationships are those we hear in the human speech ," Purves said. "That's one of the reasons people like it so much."
Read Dr. Purves and Dr. Gill's paper at the journal PLoS ONE.