Twelvenote

Twelvenote is a term used in music theory and digital music software to denote a single pitch class within the chromatic octave. In Western equal temperament, the octave consists of twelve semitones, producing twelve pitch classes that repeat with each octave. A twelvenote is typically represented by an index from 0 to 11 (often 0 = C), or by a plain pitch-class label such as C, C♯/D♭, D, and so on. In theoretical contexts, twelvenotes underlie pitch-class theory and the twelve-tone system, where collections of twelve notes form rows and sets used for analysis and composition.

In software and data models, a twelvenote is often a modular unit: a pitch class stored independently of octave information. Operations commonly associated with twelvenotes include transposition by a number of semitones, inversion, and retrograde, as well as normalizing or classifying pitch-class sets. When converting to MIDI or staff notation, a separate octave value is attached to a twelvenote to produce a specific pitch.

Originating in the study of post-tonal music in the early 20th century, the concept of pitch classes and twelve-note organization remains central to analysis, implementation, and education. The term twelvenote is not a formal standard but a descriptive shorthand used across textbooks, software documentation, and music theory discussions.

See also: chromatic scale; pitch class; twelve-tone technique; MIDI; octave equivalence.