Evidence for a universal association of auditory roughness with musical stability

Abstract

We provide evidence that the roughness of chords-a psychoacoustic property resulting from unresolved frequency components-is associated with perceived musical stability (operationalized as finishedness) in participants with differing levels and types of exposure to Western or Western-like music. Three groups of participants were tested in a remote cloud forest region of Papua New Guinea (PNG), and two groups in Sydney, Australia (musicians and non-musicians). Unlike prominent prior studies of consonance/dissonance across cultures, we framed the concept of consonance as stability rather than as pleasantness. We find a negative relationship between roughness and musical stability in every group including the PNG community with minimal experience of musical harmony. The effect of roughness is stronger for the Sydney participants, particularly musicians. We find an effect of harmonicity-a psychoacoustic property resulting from chords having a spectral structure resembling a single pitched tone (such as produced by human vowel sounds)-only in the Sydney musician group, which indicates this feature's effect is mediated via a culture-dependent mechanism. In sum, these results underline the importance of both universal and cultural mechanisms in music cognition, and they suggest powerful implications for understanding the origin of pitch structures in Western tonal music as well as on possibilities for new musical forms that align with humans' perceptual and cognitive biases. They also highlight the importance of how consonance/dissonance is operationalized and explained to participants-particularly those with minimal prior exposure to musical harmony.

Fig 1. A directed acyclic graph showing our causal model of how psychoacoustic (X, e.g., roughness) and cultural variables (culture C and mechanism M, e.g., familiarity) influence affective responses (Y, e.g., stability).

The path from X to Y is a ‘non-cultural’ effect, hence ‘universal’; the path from M to Y is a ‘cultural’ effect. However, if there is no variation in M between cultures, a cultural effect can also be ‘universal’.

Fig 2. Villages and languages (italics and shadings) in the area.

Figure from [44].

Fig 3. The relative finishedness of every chord as estimated with a multilevel Bayesian Thurstone model [67] (this model is detailed in S1 Appendix).

The dyads and triads are classified by T_n-type, which disregards timbre, transposition, and all pitches’ octaves. Each dyad’s finishedness is relative to the unison’s; each triad’s finishedness is relative to the semitone cluster’s. The units of the vertical axis are standard deviations on the normally distributed latent scale, which the Thurstone model assumes to underlie responses. The vertical scaling changes between the exposure groups to make any patterns easier to see (versions with identical scaling are available in Fig A3 in S1 Appendix). Conventional Western music-theoretical categorizations of consonance/dissonance are indicated by colour and shape. Each bar shows the 95% Bayesian credibility interval (equal-tailed) of the effect’s posterior distribution; the central shape (triangle or diamond) shows its mean.

Fig 4. Predicted effects for the five exposure groups.

Each trial had two chord pairs: the first pair was preceded by ingguk (‘one’); the second pair by yoi (‘two’). The second chord pair was the same as the first except in reverse order (hence the first and fourth chords are the same; the second and third chords are the same). After hearing these, the participant chose which of the two pairs sounded ‘finished’. The plots show the probability of choosing the second chord pair as the ‘finished’ one as predicted by the Δroughness, Δharmonicity, and Δmean pitch from the third chord to the fourth chord (all other predictors at their mean). Note that, for each predictor, because its change from the third to fourth chord is the negative of its change from the first to the second chord, it is sufficient (and possible) only to use one of these changes as a predictor. The units of Δroughness and Δharmonicity are their standard deviations, the units of Δmean pitch pitch are semitones. For each plot, the posterior mean is shown with the thick line, while its uncertainty is visualized with 100 samples from the posterior distribution. Each black dot at the bottom or top is an instance of a trial where a participant answers ‘one’ or ‘two’, respectively.