A discrete categorical pitch-gestalt, disregarding octave replication (or repetition at some other interval of equivalence) and microtonal variation within certain limits near the central pitch-area targeted by the pitch-class.
Traditionally used in 12-tone serial theory to describe the set of 12 intervals making up a row, regardless of their "octave". The pitch-classes are often designated by the set of integers 0...11.
Pitch-classes for any n-ET may be designated by the integers 0...(n-1), but this usage is normally reserved for indicating the degrees of the ET, with the concept of pitch-class being reserved for the familiar 12-part division.
Also used in my theory of finity to refer to the latitude in rational implication allowed each ratio within a periodicity block thru the employment of xenharmonic bridges.
The term pitch-class was coined by Milton Babbitt and since then has become common currency in nearly all writing concerning music presumed to be tuned in 12-edo.
Babbitt, Milton. 1960.
"Twelve-Tone Invariants as Compositional Determinants"
The Musical Quarterly, vol 46, p 247.
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