erakordset

Erakordset is a term used in music theory to denote a curated set of chords that share a particular structural property. The exact definition varies by author, but a common conception treats an erakordset as a finite collection of chords—typically triads or seventh chords—constructed or selected according to a rule or set of rules. This could involve sharing a common tone among members, belonging to a prescribed scale or key, having a restricted intervallic structure, or arising from a particular scalar or tonal system. The notion is used as an analytic and compositional tool to study relationships among chords beyond traditional functional harmony.

Construction and properties: To form an erakordset one starts from a rule or criteria, such as: all major/minor seventh chords whose roots lie in a given scale, or all triads that contain a given interval (e.g., a perfect fifth) between two members. The resulting set is examined for how its chords relate by voice-leading, shared tones, or common scale degrees, and how the set behaves under operations such as transposition within the scale, inversion, or modal rotation, depending on the formulation. Analysts consider connectivity between members, closure under chosen operations, and potential for generating musical material.

Applications: Used in analysis of tonal, modal, or atonal music, and in some compositional practices to organize harmony according to non-traditional criteria. It provides a framework for discussing chord collections that do not fit standard functional categories and can illuminate alternative paths of harmony and progression.

See also: Pitch-class set theory, chord set, non-functional harmony, set class.