# Pitch class

In music and music theory a**pitch class**contains all notess 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 pitcheses 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*:

*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*:

*n*.