Introduction

The concepts of consonance and dissonance have always been difficult to define. This is not only because every historical era has dealt with this issue differently (e.g. an interval such as the perfect fourth, which was still considered dissonant during the Renaissance but no longer so in the 17th century) but also because diverse cultural and geographic conditions have reacted completely autonomously to the same theoretical, and above all, empirical stimuli. Notwithstanding this variety and multiplicity of points of view, there are constants that we can consider “universal” about this debated controversy.

Quarta_giusta.mp3 Perfect fourth in the modern scale (equal temperament)

Definition

Generally, we define as consonant everything that sounds “pleasant” to the ear and, vice versa, dissonant whatever is perceived as an auditory “disturbance” or “tension”. Evidently, this definition is vague and approximate because: it presupposes a subjective evaluation; tension is not necessarily judged as disturbing; desire for “resolution” of tension is more a psychological rather than a theoretical need.

Historical-cultural evolution

In western music tradition, from a historical and cultural point of view, dissonance (first “practiced” and then “theorised”) began between the 15th and 16th centuries as the natural evolution of polyphonic thought; i.e. as a concept closely linked to a “multi-voice” logic, as it is the perception of a harmonic verticality, which presupposes the simultaneous playing of at least two sounds. Therefore, the need arose to insert cadences at the end of phrases that, analogically to spoken language, acted as “punctuation” (adopting the commas, parentheses, question marks, exclamation marks and quotation marks of writing punctuation in a completely different syntax). These cadences were often characterised by a dissonance that created a feeling of tension to prepare for the resolution to a consonant harmony. For an example, listen to Super flumina Babilonia by Giovanni Pierluigi da Palestrina. Over time, this practice consolidated to the point of creating a system of both harmonic tensions-distensions and unpredicted expectations and/or predictable resolutions. These strategies play a game on the listener's nerves and could easily be extend to other artistic genres such as prose or film.

For example, let's imagine a suspenseful thriller in which the predestined victim is wandering in fear in their apartment unaware of their impending fate, however, somewhat cognisant that something inescapable is about to happen. There is a knock at the door, the tension rises, the music creates the perfect atmosphere, the clueless victim opens the door and … there stands a harmless neighbour who has run out of sugar. Such a situation translated into music must generate the same suspense and the composer uses cadences and a balance of dissonance and consonance to direct the events.

Perceptual and psychoacoustical universality

Of course, all of this functions perfectly within a logic that is strongly anchored in tonality; i.e. a thought born in Western culture between the 16th and 17th centuries that persists to this day, albeit with a few flaws. However, other civilisations (think of African, Arabic or Asian music) move in completely different semantic backgrounds, which are very far from the linguistic dynamics of tonal logic. Despite this, there are “universal” laws that we could extend to every era and culture because they are linked to the physiology of our auditory apparatus and the physical properties of all vibrating bodies. It is not by chance that the base of every civilisation rests on the interval of the perfect fifth; i.e. the distance between the second and third partial of a series of harmonics. It is also not by chance that tonal syntax was born and developed from the major triad formed by the superimposition of the first 5 to 6 harmonic partials.

Quinta_giusta.mp3 Perfect fifth in the modern scale (equal temperament) Triade_maggiore.mp3 Major triad in the modern scale (equal temperament)

Conclusions

Today, physicists, musicians and acoustic engineers are trying to find the laws that unequivocally establish this hierarchy. However, the underlying problem that renders much of this research in vane or questionable is that the perception of consonance depends on so many parameters that they cannot be easily kept under control (the musical context, the register in which the musical instruments are playing, the relationship between instruments with different timbres, etc.) making any type of univocal determination almost impossible.

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