The Beautiful Journey of Just Intonation Music

There has always been one fascinating topic in my musical life: Just Intonation (JI) music.

At first, I was attracted to microtonal music. I felt like different parts of my brain, or even emotions I wasn’t really familiar with, were being evoked by it. I was experiencing how “different structures of frequencies could affect my body and mind differently.”

Then one day I saw a random short video on YouTube. I forgot what the content was about, but the music hit me differently. It was hard to describe that feeling, a kind of strong resonance. I searched for the original artist, who is called Aloboi, and saw he was playing a piece comparing 12-TET and JI. The visualization was obviously different. Due to the equality of 12-TET, the oscilloscope is always unstable, while the pure ratios of JI remain stable in certain chord combinations.

I wondered: is this the reason I feel more in resonance? Is this why people feel peaceful around singing bowls or tuning forks, because they consist of simple integer ratios? All these questions led me to a journey of JI exploration.

What “Roughness” Actually Means

There’s still room to debate what the perfect tuning system is, and I believe maybe we don’t need a perfect one. Good music involves too many factors across various dimensions. For this discussion, I’ll focus on the physical effects and cognitive influences.

The biggest difference between 12-TET and JI is how they define notes. 12-TET equally divides the octave into 12 notes, while JI defines notes based on simple integer ratios. This means all chords in 12-TET (except the octave) are dissonant, in other words, contain more “roughness”.

In the studies of Plomp & Levelt (1965), they defined roughness as a biological phenomenon: when two frequencies are too close, the Critical Bandwidth (CBW) in the cochlea can’t separate them, creating fast beats. When the beats speed up beyond 20–30 Hz, they cause an uncomfortable physical sensation, that’s roughness. It creates dissonance between 15–300 Hz, peaking at 25% of the CBW.

This discomfort is hypothesized to come from a synchronization failure between the auditory system and neural firing (Villegas & Cohen, 2010), creating chaotic signals that increase computational load for the brain (Bidelman & Krishnan, 2009). Simple integer ratios create more stable structures, leading to a perfect “mode-locking” synchronization in the brain (Lots & Stone, 2008).

Is It Just Cultural Habit?

JI music sounds odd to some people’s ears. At least some of my musician friends say so.

As I mentioned, good music involves many factors, and one of them is the complexity of cultural acquisition. Being used to a system can sometimes impact us more powerfully than the physical roughness disturbances. Scientists have found ways to exclude cultural acquisition: one is testing babies, another is testing native Amazonians.

In the studies of Zentner & Kagan (1996), they tested babies (4–6 months) for their natural responses to “consonance” and “dissonance” sounds. The babies had longer looking time for consonant sounds, and showed more motor activity (an annoyance response) for dissonant ones. This proved a point that humans have an innate preference for consonant intervals.

Some people questioned this: “the baby might already be influenced before birth, or they just learn very fast within a few months.” So McDermott et al. (2016) did a specific study on native Amazonians, who have never learned Western music, and whose traditional music has no polyphony, so they don’t even have the concept of chords. The results showed that they all had an innate aversion to rough sounds, but they did not show preference for more consonant intervals.

These two studies showed that dissonant sounds are a universal biological discomfort for humans, but there’s not strong enough evidence for a positive relation between consonance and preference.

Timbre Changes Everything

So what truly matters? Is it the frequency, the tuning system, or the timbre?

William A. Sethares offers an interesting perspective by focusing on the relationship between timbre and tuning. In his book Tuning, Timbre, Spectrum, Scale (2005), he argued that:

“Consonance and dissonance are not inherent qualities of intervals, but are instead dependent on the interaction between the spectrum (timbre) and the tuning (scale) of the sound.”

In other words, the harmonic series of the notes have to be aligned with the tuning. Every different material has different physical characteristics, and that changes the harmonic series, such as strings, stones, woods, they are all different.

In his experiment with Gamelan, he found that the Slendro scale is very different from Western ones, but it doesn’t sound dissonant, because the scale matches the special harmonic series of its bronze metallophones. It sounds awful in a normal Western scale. This extends the concept of roughness, but still proves how frequencies sound bad when the harmonics have a beating effect.

Sethares’ experiment made me think: maybe there won’t be a perfect tuning system. The point is not stiff interval relations. It’s about the whole structure.

From JI to Roughness

After diving into all of this, my thinking shifted.

JI was where I started, the visual stability on the oscilloscope, the feeling of resonance, the simple integer ratios. But the more I read, the more I realized that what’s really going on isn’t about JI being “the right answer.” It’s about something deeper: roughness, and how the body responds to it.

JI is one way to lower roughness. But it has its own problems, like wolf intervals. What truly matters is whether the harmonics fight or align, whether the brain has to work or relax.

That’s why my research direction is moving toward roughness itself, not just JI. Most experiments so far focused on preference, which is subjective, and some still compare dissonance and consonance within the scale of 12-TET. I want to dig deeper into the cognitive load of low-roughness spectra and lower beating effects, for my further research.

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References

1. Bidelman, G. M., & Krishnan, A. (2009). Neural correlates of consonance, dissonance, and the hierarchy of musical pitch in the human brainstem. The Journal of Neuroscience, 29(42), 13165–13171.
2. Shapira Lots, I., & Stone, L. (2008). Perception of musical consonance and dissonance: An outcome of neural synchronization. Journal of the Royal Society Interface, 5(28), 1429–1434.
3. McDermott, J. H., Schultz, A. F., Undurraga, E. A., & Godoy, R. A. (2016). Indifference to dissonance in native Amazonians reveals cultural variation in music perception. Nature, 535(7613), 547–551.
4. Plomp, R., & Levelt, W. J. M. (1965). Tonal consonance and critical bandwidth. The Journal of the Acoustical Society of America, 38(4), 548–560.
5. Sethares, W. A. (2005). Tuning, Timbre, Spectrum, Scale (2nd ed.). Springer-Verlag.
6. Villegas, J., & Cohen, M. (2010). Roughness minimization through automatic intonation adjustments. Journal of New Music Research, 39(1), 75–92.
7. Zentner, M. R., & Kagan, J. (1998). Infants’ perception of consonance and dissonance in music. Infant Behavior & Development, 21(3), 483–492.