How Brain Chemistry May Explain The Appeal of Sweet Harmonies

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A century has passed since composer Arnold Schoenberg and his disciples rejected tonal harmonies, yet Schoenberg’s music is still considered by many to be “difficult” at best, and utter cacophony at worst.

Is this because the dissonances in Schoenberg’s atonal compositions conflict with some fundamental human preference for consonance, embedded in the very way we perceive musical sound?

That is what his detractors have sometimes implied, and it might be inferred also from a new scientific model on human response to consonance and dissonance developed by Bernardo Spagnolo, a biophysicist at the University of Palermo in Italy, and collaborators at Lobachevsky State University of Nizhni Novgorod in Russia. Their research is reported this month in Physical Review Letters.

Spagnolo and his colleagues suggest that a preference for consonance may be hard-wired into the way we hear music. They maintain that we humans have different neurons in different parts of our ears that respond to different frequencies. Say perhaps one group responds to a C on a piano, and another to an E, etc. These are called sensory neurons. But that’s not enough to account for “liking” the two played at the same time.

Indeed, the researchers note that we also have a third type of neuron called an interneuron. In their model, the sensory neurons send signals to the interneuron, which then sends signals based on what is “heard” from them to the brain.

Quantitative analysis shows what happens next. When the sensory neurons were fed consonant chords like a major third on a piano, the interneuron produced an output signal consisting of regular, well-shaped peaks. Dissonant chords, which result in a higher level of disorder in the interneuron output, made the signal blurry. In other words, neural signals are smooth and predictable for pleasant-sounding frequencies, but are erratic for those that are not.

A Repudiation of Atonality?

One could interpret this as a rationalization for the very choice of major and minor chords in Western music. This conclusion is not entirely new. The Canadian neuroscientists Shapira, Lots and Stone proposed in 2009 that a preference for consonance may be hard-wired into the way the brain processes music.

Some music historians have also suggested that a tonal framework was always implicit in Schoenberg's music. Leonard Bernstein argued in his Harvard Lectures that Schoenberg, even in his most atonal works, harbored a nostalgic yearning for the hierarchy of Western tonality. But where does this leave music built on non-Western harmonies – be it Indian ragas, the mbira music of Zimbabwe or the gamelans of Indonesia? Do these sophisticated art forms produce disorder? And what about other formal structures in music, such as the regularity of rhythm? Are our brains purely attuned to harmony alone, without respect to other parameters? 

"This is progress," André Longtin of the University of Ottawa told the journal Physical Review Focus. "But I wouldn't say that it has nailed the problem shut."

Weigh in: do you think our brains respond naturally to pleasing harmonies? Or is there an element of adaptability at work?