Consonanza e dissonanza en
From "Physics, Waves, Music": a website about the physics of waves and sound, acoustics of musical instruments, musical scales, harmony and music.
Introduction
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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 considered consonant in medieval polyphony and became a dissonance above the bass in the Renaissance) 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. |
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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 Babylonis 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
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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 (harmonics 4, 5 and 6, in the ratio 4:5:6). Why these intervals in particular? When the frequencies of two notes are in a simple ratio, many harmonics of one coincide with harmonics of the other; if the ratio is complicated, harmonics that are close but do not coincide produce fast beats, which the ear perceives as roughness. This explanation, due to Helmholtz, is discussed on the page Physical and mathematical aspects. |
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Conclusions
Today, physicists, musicians and acoustic engineers are trying to find the laws that unequivocally establish a hierarchy of consonant intervals. However, the underlying problem that renders much of this research vain 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.
Check your understanding
The perfect fourth was considered consonant in medieval polyphony and dissonant in the Renaissance when it lies above the bass. What does this tell us about consonance?
Answer. That the judgement of consonance or dissonance depends partly on the era and on the cultural and musical context, and not only on the physical properties of the interval.What was a dissonance in a cadence for?
Answer. To create tension and expectation at the end of a phrase, and then resolve it on a consonant harmony: like punctuation in spoken language, the cadence marks the conclusion of a musical period.A string has its fundamental at 100 Hz. Between which of its harmonics is there an interval of a perfect fifth, and which harmonics form a major triad?
Answer. The perfect fifth is the interval between the second and the third harmonic (200 and 300 Hz, ratio 3:2). The major triad is formed by the fourth, fifth and sixth harmonics (400, 500 and 600 Hz, ratio 4:5:6).Why do almost all civilisations use the perfect fifth, even though their music is very different?
Answer. Because its consonance depends on physical and physiological facts common to everyone: the harmonics of every vibrating body and the way the ear perceives them. In the perfect fifth many harmonics of the two notes coincide and do not produce beats.In-depth study and links
- The physical explanation of consonance, from Galileo to Helmholtz, is on the page Physical and mathematical aspects; the perceptual point of view on the page Critical bands.
- The role of consonances and dissonances in building a harmonic syntax is discussed on the page Psychoacoustic and musical aspects.
