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In music and music theory a
pitch class contains all notes that have the same
name; for example, all Es, no matter which octave they are in, are in the same pitch
class.
In musical set theory it is more accurate to say that a
pitch class is an equivalence class of all pitches that are octaves apart, which would be labeled by an integer, not a traditional letter name. In both cases, when "pitch class" is used, the use of
"pitch" indicates a specific frequency or note and does not include its
octaves.
Using integer notation and Mod 12, two pitches, x and y, are in
the same pitch class only if for some integer n:
- x = 12n + y
If one only knows the pitch interval, ip, between
two pitches, one may use this definition: A pitch class is the set of all pitches such that
for any to members of the set x and y:
- ip(x,y) = 12n
for some non-negative integer n.
See also
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