There is Peace in Harmony

Maybe you can’t stop listening to the pop-harmonies of Taylor Swift or perhaps you find yourself enjoying the elusive “up-and-coming” SoundCloud rappers. Regardless, even with these dissimilarities, we can all agree on the fact that some chords sound ‘good’ and others notes brawl when they’re played at the same time outlining the idea of consonance versus dissonance.

Figure 1. (A) represents a consonant interval while (B) represents one of dissonance. Solid lines indicate the frequency components of the root note; dotted lines represent the frequency components of the interval note.

Music is a universal human phenomenon. An understanding of the underlying auditory processing concerned with listening to music may unravel which musical parameters are innate in our biology. Behavioral studies have shown that listeners prefer consonant intervals and assign them a higher status in hierarchical rankings (Plomp and Levelt, 1965). It is this hierarchical organization of pitch that contributes to the sense of a musical key and pitch structure in Western music (Rameau, 1722).

In any case, the question remains: why is it that we prefer consonance over dissonance? Bones et al. (2014) hypothesized that the perception of consonance can be accounted for by the neural representation of harmonicity (the closeness of fit of two notes). To test their hypothesis, participants were presented with dyads (two-note chords) made up of a lower note (the ‘root’) and a higher note (the ‘interval’) and asked to rate them on their pleasantness or unpleasantness.

To test the effects of interactions within the cochlea, researchers also measured the electrophysiological frequency following response (FFR). FFRs are neural signals generated in the brain when people hear sounds as measured by frequency components. FFRs were recorded in two scenarios: when each dyad was presented to both ears (diotic) or one note assigned to each ear (dichotic). To measure the strength of the representation of harmonicity, a neural consonance index (NCI) was calculated giving a quantitative look into how consonant a dyad is
perceived.

Figure 2. Schematic of dichotic vs. diotic listening tasks.

The results of this study establish that average dyad pleasantness ratings are consistent with prior studies in that consonant dyads were more pleasant over dissonant dyads (Bidelman and Krishnan, 2009; McDermott et al., 2010). Consonance preference for differing intervals was found to have a close correspondence to the neural representation of harmonicity as reflected in the FFR. Additionally, when the dyads were presented to both ears, the perception of consonance was higher than when the two notes were presented to separate ears. The FFR showed a stronger representation of harmonicity in the diotic scenario and interactions between the harmonics of the two notes on the basilar membrane of the cochlea resulted in further frequency components being present in the FFR. Therefore, a diotic scenario enhances the consonance of a sound. Overall, the research suggests that a preference for consonance depends both in part by the neural representation of harmonics as well as their cochlear interactions.

One weakness of this study is its specificity to Western music. In a study of Tsimane’s – a native Amazonian society – in comparison to Western culture found that cultures sufficiently isolated from Western music are devoid of consonance preference (McDermott, 2016). Thus, it is unlikely that there is an innate bias toward harmonic sounds (McDermott, 2016). However, there are conflicting studies regarding infants’ ability to show preference for consonant sounds (Trainor, 2002) that suggest that it is indeed innate. There is no conclusion in Bones et al. (2014) regarding the innateness of consonance preference. The confliction of these studies leads to confusion in their conclusions.

In general, this study provided great insight into the neural components of what makes consonance sound so right. Though we may not be able to figure out if this is innate or learned, it can at least be agreed upon that Westerns find more peace in harmony.

 

References 

Bidelman GM, Krishnan A (2009) Neural correlates of consonance, dissonance, and the hierarchy of musical pitch in the human brainstem. Journal of Neuroscience 29(42):13165-13171. doi: 10.1523/JNEUROSCI.3900-09.2009 

Bones O, Hopkins K, Krishnan A, Plack CJ (2014) Phase locked neural activity in the human brainstem predicts preference for musical consonance. Neuropsychologia 59:23-32. doi: 10.1016/j.neuropsychologia.2014.03.011

McDermott JH, Hauser MD (3005) The origins of music: Innateness, uniqueness, and evolution. Music Perception 23(1):29-59. doi: 10.1525/mp.2005.23.1.29

McDermott JH, Schultz AF, Undurraga EA, Godoy RA (2016) Indifference to dissonance in native Amazonians reveals cultural variation in music perception. Nature 535:547-550. doi: 10.1038/nature18635

Rameau JP (1722) Treatise on harmony. Reprint. New York: Dover, 1971

Plomp R, Levelt WJM (1965) Tonal consonance and critical bandwidth. Journal of the Acoustical Society of America 38:548-560. doi: 10.1121/1.1909741

Trainor LJ, Tsang CD, Cheung VHW (2002) Preference for Sensory Consonance in 2- and 4-Month-Old Infants. Music Perception 20(2):187-194. doi: 10.1525/mp.2002.20.2.187

Pictures

Figure 1: Bones O, Hopkins K, Krishnan A, Plack CJ (2014) Phase locked neural activity in the human brainstem predicts preference for musical consonance. Neuropsychologia 59:23-32. doi: 10.1016/j.neuropsychologia.2014.03.011

Figure 2 Girl: (https://www.vectorstock.com/royalty-free-vector/person-with-headphones-icon-image-vector-14803217)

Figure 2 Music notes: (https://en.wikipedia.org/wiki/Musical_note)

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