The simultaneous sounding of two or more tones which, because of beats,
seems unpleasant to the human ear. Which musical intervals
are considered dissonant is largely a matter of cultural and historical
relativism. For instance, some intervals regarded as dissonant in the Medieval
period were found to be consonant during the Renaissance. Also, the way
a dissonance is resolved (and even the way it is orchestrated) can decrease
or intensify how harsh it sounds. Intervals commonly considered dissonant
in tonal music are the major and minor seconds and sevenths.
A dissonant chord, or dischord, is a chord
that sounds incomplete until it resolves itself on a harmonious chord.
See also suspension.