A music-theory concept that groups all pitches sharing the same pitch name into a single equivalence class, abstracting away octave and timbre. Developed within 20th-century atonal theory (Schoenberg, Forte), it serves as the foundation for pitch-class set theory, where sets of pitch classes (called pitch-class sets) are analyzed by their interval content. Pitch classes are typically numbered 0–11 (C=0, C#=1, ..., B=11). [formal: classis-tonalis | substrate: mind | horizon: a life | explicit: yes | epoch: 1.00]
Accepted ontology entry
pitch-class
A music-theory concept that groups all pitches sharing the same pitch name into a single equivalence class, abstracting away octave and timbre. Developed within 20th-century atonal theory (Schoenberg, Forte), it serves as the foundation fo…
Definition
Why it is in scope
A human-made music-theory concept that groups all pitches sharing the same pitch name (or related by octave equivalence) into a single equivalence class. Developed within 20th-century atonal theory and set theory, it abstracts away octave and timbre to focus on pitch relationships, forming the basis for pitch-class sets and tone rows.
Names and aliases
- pitch-classen · CANONICAL
Relations from this entry
- cmsoqq3ec02lqjlssdy5o9rzdDEPENDS_ON →
pitch-class needs pitch to operate: it categorizes pitches by their equivalence classes. Remove the concept of pitch (the perceptual attribute of how high or low a sound is) and pitch-class loses its operative basis — you cannot group by pitch name without the concept of pitch itself. The removal test passes: without pitch, pitch-class cannot function.
Relations to this entry
- cmsqzptf2007jswynsrg45snc← DERIVED_FROM
Pitch-class is the 12-tone theoretical concept from Western music theory (centuries old). Chroma is a 12-dimensional feature vector that encodes pitch-class energy distribution — it was designed to represent pitch-class information in audio analysis. Chroma derives from and implements the pitch-class concept.
- cmsqzptf2007jswynsrg45snc← INSTANCE_OF
Chroma is a specific pitch-class representation: it folds all octaves of the pitch spectrum into 12 pitch classes, representing the equivalence of pitches separated by octaves in music. Chroma is a particular form of pitch-class encoding.
- cmsrn4a2j000sbesrwswpvirk← DEPENDS_ON
Chroma features operate by folding spectral energy onto pitch-class bins. Remove the pitch-class concept and the projection has no target — chroma features stop operating entirely. This is not meta-level (they need naming); the pitch-class partition is the structural skeleton of the representation itself.
- cmsqzptf2007jswynsrg45snc← DEPENDS_ON
Chroma features compute spectral energy distributed across 12 pitch-class bins. Remove pitch-class and chroma has no bins to partition energy into — its entire operation depends on the pitch-class concept. This is constitutive, not just historical: pitch-class is the organizational structure chroma computes upon.
Record identity
- Created
- Aug 13, 2026, 3:30 AM UTC
- Content hash
- 71adee8b2588731f6b1d5a55ac843ffe4e28c2053fd373966954ca01e862e8cb