This post concludes with a three-part survey of musical embodiment—the idea that music is not just a mental experience, but one that involves our entire body—and how this physical connection shapes our musical preferences. Last month’s message a predictive coding model that asserts that musical preferences are learned and therefore largely cultural. Because this learning occurs in the cortex, the most advanced areas of the brain, it is called a “top-down” model.
We now turn to neural resonance theory, which suggests that our musical preferences are innate and deeply biological. This is a “bottom-up” model because much of the processing of the sound we hear begins early—in the inner ear and brain—along the auditory (hearing) pathway. (Note: this post explores melody; rhythm will be the focus of a future post.)
We are in sync with the music
Consider this quote as the motto of Neural Resonance Theory (NRT): “Your brain and body are literally in sync with the music.”1
Musical notes, like all sounds, are created by the vibrations of air molecules. When these vibrational waves reach the cochlea (the sound-detecting organ of the inner ear), they activate it to fire signals in sync with the frequencies of the notes.
We measure sound frequencies in cycles per second, or Hertz (Hz), named after the physicist Heinrich Hertz. The cochlea converts the mechanical vibration of the air molecule into an electrochemical signal firing (called resonance) at the appropriate frequencies.
For example, A concert, the note that the orchestra plays to, is A above middle C. It is marked A4 and has a frequency of 440 Hz. The part of your cochlea that detects A4 converts its mechanical sound waves into electrochemical nerve signals that fire or resonate at the same frequency.2
This incredible ability to detect and transform frequencies allows our auditory system to separate notes. There can be no melody without it.
Upon exiting the cochlea, these electrochemical signals travel along the auditory nerve to the brain stem. They then travel up the brain stem, pass through the thalamus, and reach the primary auditory region of the temporal lobe of the brain. Nerves all along this path fire at frequencies that match musical notes. you nervous system thus being dynamic and physically in tune with the music of its environment.
The math behind the sounds
A melody is a sequence of different musical notes. Since neural signals reflect sound frequencies, we can map the relationships between musical notes using mathematical correlations:
The note-to-note ratio one octave above that is 2:1 (A5 frequency 880 Hz). The ratio of the note to the fourth above (A4 to D5) is 4:3 (D5 frequency 586.67 Hz) and to the fifth above it (A4 to E5) 3:2 (E5 frequency 660 Hz). This and other simple correlations are usually experienced as pleasant or consonant.
Compare this with the ratio of the major seventh (A4 to G♯5), 15:8, and the tritone (A4 to D♯5), 45:32.3 These and other complex ratios are often felt as harsh or unfavorable.
According to NRT, our brain naturally favors smooth, simple correlations (consonance) and rejects clashing, complex correlations (dissonance).4 This does not mean that it is always opposed to dissonance – music that is only consonant boring. Instead, our brain can enjoy the tension of dissonance as long as it is brought back into harmony.
Thus, the brain expects to solve the problem because of its innate biology, not because it has learned to do so. This explains why you can listen to the same song for the hundredth time and love it – your neural circuits synchronize with its strange musical patterns (resonances), even though you know the song well, you no longer make predictive errors about it.5
Edward Large, Ph.D., professor of physics and psychology at the University of Connecticut, is a pioneer of NRT. He and his colleagues argue that we don’t just count what note comes next; rather, the dynamics of our brains physically reflect the structure of the music. Initially drawn to NRT because of its elegant mathematics, Dr. Large points out that these mathematical ratios are not abstract concepts—they are actual rates of fire in your nervous system.6
Essential Readings in Neuroscience
How resonance creates emotions and feelings
Both the predictive coding model (PCM) and NRT activate the limbic system to generate emotions (feelings and emotions), but each does so in its own way. In PCM, instructions based mainly on learned musical preferences are transmitted to the limbic system to act on it. With NRT, physical resonances of neural signals originating from and matching the notes of a musical source flow through pathways that activate the limbic system.7
When the limbic system is activated, likes and dislikes are realized in NRT in the same way as in PCM: by releasing neural and chemical signals that produce embodied feelings and emotions.8 Thus, NRT is dually embodied: the resonances that resonate with musical notes and the sensations felt on the brain map of the body.
Evolutionary priority
How does the innate recognition of tone, the resonant ratio of musical tones, benefit people? Consider these two survival values. First, speed: just as certain combinations of sounds indicate natural danger, like a predator in a bush, a quick reflex response allows your body to react and jump away before your conscious brain can even register what the sound is. Second, attention: the world is full of cluttered background noise, and melodies serve as a fresh auditory anchor that helps the brain filter out the static and focus on what’s important.
Summary
So which approach is correct: predictive coding or neural resonance theory? Do our musical preferences come from cultural learning or biological wiring? The answer is probably a combination of both.
As noted neurologist Norman Geschwind wrote, complex human behavior requires a genetic background that makes that behavior possible and brings it to life, along with instruction and actual practice.9 And in keeping with the theme of this three-part series, both approaches rely on the notion of embodiment, that music is an interactive experience between our brains and our bodies.
