The sensation that the two notes in an interval or the many notes in a chord do not blend or fuse into a sound that seems to be 'at rest', so that they seem to have an "active" quality in which each component remains audibly distinct.
It is one pole of the continuum of musical accordance, the other pole being that of concordance.
A conglomeration of pitches can be said to be a discord based strictly on psychoacoustic phenomena, and regardless of any use of that particular conglomeration in a musical context. For the latter, see sonance.
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