Chordioid

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A chordioid is a small group of notes that doesn’t count as a full chord by normal theory, but is useful as a base for making other chords. Most chordioids avoid semitones, so the scales they point to can stay smooth and consistent; some can still include semitones.

The main use of a chordioid is to add one or more notes to the base to form “legitimate” chords in 12-tone equal temperament. From the same base, different added notes can produce many different chords. The notes can also move together in small steps, so related chords can be reached by moving just one voice.

Practically, teachers and players learn chordioids the same way they learn chords: in all keys, ranges, inversions, and voicings, for reading, writing, and playing. A familiar chord can itself be used as a chordioid to create new chords, too.

A common example is the Italian augmented sixth chord (It+6). By adding one more note, you can get the French (+6) and German (+6) augmented sixth chords. The idea has roots in the work of composers like Satie, Debussy, Ravel, and Fauré, and it found its way into jazz through Bill Evans.

Two chordioids can be combined, though duplicating notes often reduces the number of distinct pitches. Chordioids relate to polychords (which also come from combining chords) and to upper-structure ideas and slash chords, but chordioids start from a shared base rather than freely picking tones.

The “master chord” idea, named by Nicolas Slonimsky, describes a representative chordioid such as 7no5 (for example, C, D, F#). Its sound can resemble that of It+6 in some contexts. The term emphasizes technique and usefulness rather than any missing notes or specific harmonic function.

There are many forms of chordioids arising from altering or omitting notes in seventh chords (for example, 7no3, M7no3, 7♭5no3, and others). Some forms align with the symmetry of the whole-tone scale, giving distinctive textures and colors. The concept is also used by composers and theorists like Schillinger to build larger musical textures, using triads and master chords as basic chordioids.