Dissonance In Music

Definition

Throughout history, dissonance has been given many different definitions. Even today, different dictionaries and encyclopedias will give varying descriptions, including 'an inharmonious or harsh sound', 'an unresolved musical note or chord', 'unstable intervals', and 'disagreeable effect produced by certain intervals'.

In essence though, dissonance is used as part of a system of tension and release, or push and pull between dissonant and consonant sounds. Historically considered unpleasant, dissonances were later looked at as 'unstable' with a need to resolve, and later still used very frequently and more visibly. All of these approaches, from the subtle to the harsh are used to give the impression of beauty, emotion, and expressiveness in music. Dissonances apply to harmony, chords and intervals, and can be momentary and fleeting, or more persistent, as is often the case with more modern music. Harmony in Western tonal music is based on a hierachy of chords called triads. Some of these chords are considered more or less dissonant than others, and the creative use of these chords gives our music is structure.

Use of Dissonance Throughout History

 In pre-medieval times, only perfect 4th's, 5th's and octaves were consonant. All other intervals were considered dissonant, and this theory prevailed into the Middle Ages, where religious significance was given to the perfect intervals. These intervals were considered 'godly' and 'holy', and all others were termed 'imperfect' (major and minor terminology had yet to be invented). Early polyphony moved in parallel octaves, 4th's and 5th's, and what we now call the major 3rd and 6th were considered dissonant, and were not used. This is contrary to the common practice period where 3rd's and 6th's are most consonant, with perfect 4th's, 5th's and octaves considered hollow sounding when heard in succession.

In early Renaissance music, intervals such as the perfect fourth were considered dissonances that must be immediately resolved. The regola delle terze e seste ("rule of thirds and sixths") required that imperfect consonances should resolve to a perfect one by a semitone progression in one voice and a tone progression in another.

Any note that doesn't fall within the prevailing harmony is considered dissonant, and this was used to great effect by composers of the common practice period in the form of ornaments. Ornaments were used to create brief dissonances to add interest and colour and to decorate the music. Dissonances on strong beats are especially potent - suspensions and appogiaturas are both examples of ornaments that place a strong and relatively lengthy dissonant emphasis on a strong beat of the bar. Ornaments, like all dissonances at the time, always resolved to a consonance. Momentary dissonances also occur with notes of melodic decoration, such as passing notes and auxiliary notes.

In the 19th century, composers such as Brahms, Strauss and Wagner were much freer in their use of dissonance. As time went on, listeners adapted to the dissonance heard in music, and composers compensated for this by strengthening the level of dissonance, and the old dissonances now became consonances. This is something that has happened throughout history; consider Beethoven's Ninth Symphony - very pleasant to the ear of a modern listener, but was considered dissonant by many of his contemporaries, and some blamed this presumed 'mistake' on his deafness. The idea of sustained dissonance was bought to its peak by Arnold Schoenberg when in the 20th century he spoke of 'emancipation of the dissonance', in that there is no difference between consonance and dissonance, or the distinction between the two is blurred. The result of this is atonal music, where consonance is all but abandoned.

Although the extent of what is or isn't dissonant has changed over time, the purpose of it has stayed the same; to generate tension, and thus interest in the music, and to add colour. The definitions and conventions of usage related to dissonance also varies widely among different styles, cultures and traditions. The basic idea of dissonance, consonance and resolution exist in some form in all music that has a concept of melody, harmony and tonality. There has been a clear historical progression towards the acceptance of more and more dissonance in our music, but this progression has been gradual as audiences acclimatize to dissonance, and composers strive for something new.