Pitch class

In music, a pitch class (p.c. or pc) is a set of all pitches that are a whole number of octaves apart; for example, the pitch class C consists of the Cs in all octaves. "The pitch class C stands for all possible Cs, in whatever octave position."[1] Important to musical set theory, a pitch class is "all pitches related to each other by octave, enharmonic equivalence, or both."[2] Thus, using scientific pitch notation, the pitch class "C" is the set

{Cn : n is an integer} = {..., C−2, C−1, C0, C1, C2, C3 ...}.
\override Score.TimeSignature #'stencil = ##f
\relative c' {
  \clef treble \key c \major \time 4/4
  <c c'>1
} }
Perfect octave
\override Score.TimeSignature #'stencil = ##f
\new PianoStaff <<
\new Staff \relative c' {
  \clef treble \key c \major \time 4/4
  <c' c' c'>1 \bar "|."

\new Staff \relative c' {
  \clef bass \key c \major \time 4/4
  <c c, c, c,>1
} >> }
All Cs from C1 to C7 inclusive

Although there is no formal upper or lower limit to this sequence, only a few of these pitches are audible to humans. Pitch class is important because human pitch-perception is periodic: pitches belonging to the same pitch class are perceived as having a similar quality or color, a property called "octave equivalence".

Psychologists refer to the quality of a pitch as its "chroma".[3] A chroma is an attribute of pitches (as opposed to tone height), just like hue is an attribute of color. A pitch class is a set of all pitches that share the same chroma, just like "the set of all white things" is the collection of all white objects.[4]

Note that in standard Western equal temperament, distinct spellings can refer to the same sounding object: B3, C4, and Ddouble flat4 all refer to the same pitch, hence share the same chroma, and therefore belong to the same pitch class. This phenomenon is called enharmonic equivalence.

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This article uses material from the Wikipedia article Pitch class, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.