Dissonance

In music, dissonance is the opposite of consonance. Both are words applied to harmony: sounds which are dissonant seem unstable, and have an aural need to resolve to a stable consonance.

In general the closer the frequencies of two pitches (notes without any overtones) the more dissonant they are. As two pitches approach each other they begin to produce beat oscillations, which are caused when the two pitches cause interference, or reinforce and cancel each others amplitudes.

Dissonance has been defined differently by different people in different places at different times. Western musical history can be seen as progessing towards a wider definition of consonance, culminating in the emancipation of dissonance, such as in the view of Arnold Schoenberg.

While, as can be seen from the above paragraph, the perception of dissonance is obviously culturally influenced, dissonance also seems to have some objective basis. Consonance between two notes can be defined as greater coincidence of their harmonics or partials, which collectively are overtones. Dissonance is then defined by the amount of beating between non-common harmonics.

In poetry, dissonance is the deliberate avoidance of patterns of repeated vowel sounds (see assonance).