interval (music)

In music theory, the term interval describes the difference in pitch between two notes. Although frequently used in connection with intervals, the term "distance" does not adequately describe the physics and subjective effects of two interacting frequencies.Intervals may be described as:vertical (or harmonic) if the two notes sound simultaneouslylinear (or melodic), if the notes sound successively.Interval class is a system of labelling intervals when the order of the notes is left unspecified, therefore describing an interval in terms of the shortest distance possible between its two pitch classes.
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