pitch class set theory

Pitch class set theory is a way music theorists analyze and organize groups of pitches based on their relationships, regardless of octave differences. It treats all pitches that are the same note across different octaves as equivalent, called a "pitch class" (e.g., all C's). By examining the collection of these pitch classes as a set, theorists can identify patterns, structures, and transformations within music, like transpositions or inversions, providing insight into a piece’s underlying harmony and structure without focusing on specific octave placements.