Chromatic Mediant¶
A strict one-common-tone relation between same-quality major or minor triads whose roots lie a third apart.
Core Idea¶
A chromatic mediant is a relationship between two chords. Under the strict convention used here, both chords are major or both are minor, their roots lie a major or minor third apart, and they share exactly one pitch class. For example, C major {C, E, G} and A-flat major {A-flat, C, E-flat} are both major, their roots are a third apart, and C is their only common pitch class. A major or minor triad has four such partners: above and below by either size of third.[^ref-6cc8a6456404]
The label tells us how the chord pair is related. It does not by itself tell us how the music is voiced, whether the key changes, or what feeling the passage conveys. Some writers use the name more broadly; Kopp separates zero-common-tone disjunct mediants from this strict group, while Lee includes some disjunct examples in a broader discussion.[ref-6cc8a6456404][ref-70908b3474c9]
Scope of Application¶
The test applies to major and minor triads in tonal music. The chords can be next to each other in a cue or meet across a movement boundary. Count their pitch classes rather than asking whether one musician physically sustains the shared note. The same relation can have different functions in different works.[ref-6cc8a6456404][ref-70908b3474c9]
Kopp's scheme includes both major-third and minor-third root distances and both major and minor starting triads. Lee's two named works below show the major-to-major, descending-major-third subtype; they do not alone demonstrate every member of the larger class.[ref-6cc8a6456404][ref-70908b3474c9]
Clarity¶
Check three things in order: Are both chords the same quality? Are their roots a third apart? Do they share exactly one pitch class? C major to E minor fails the first and third tests: it changes quality and shares E and G. C major to E-flat minor has no shared pitch class. Naming the strict convention makes those boundaries clear.[^ref-6cc8a6456404]
Manages Complexity¶
Many third-related chord pairs are possible. Kopp sorts them by common tones: relative mediants share two, strict chromatic mediants one, and disjunct mediants none. Root direction and major- or minor-third distance distinguish the four strict partners of a reference triad. That simple classification lets an analyst compare differently voiced or orchestrated passages while keeping interpretation of key and affect separate.[^ref-6cc8a6456404]
Abstract Reasoning¶
Write down the two triads' pitch-class sets, roots and qualities. Test the third interval and matching quality, then find the intersection of the sets. Exactly one shared pitch class means the pair qualifies under this convention. A chord with an added seventh needs a declared choice: classify its underlying triad or analyze the full sonority separately. The chord-pair test cannot by itself prove a modulation or an expressive meaning.[^ref-6cc8a6456404]
Knowledge Transfer¶
The same test works on Bach's movement transition and Goodman's film cue because the required chord-pair roles can be identified in both. Their musical purposes differ, so a cadential or dramatic interpretation from one does not automatically transfer to the other.[^ref-70908b3474c9] The broader structural parent is Relation: this is a binary relation on triads with an explicit membership rule. Major/minor quality, root thirds and shared pitch content keep the named identity within music theory.
Example¶
Bach, Brandenburg Concerto No. 3: Lee identifies B major at the end of the brief second movement and G major at the start of the third. Their roots descend a major third. B major {B, D-sharp, F-sharp} and G major {G, B, D} share only B. The pair qualifies even though it crosses a movement boundary.[^ref-70908b3474c9]
Goodman's Dirty Rotten Scoundrels cue: In Lee's analysis of a scene where a character appears to regain the ability to walk, E major moves to C major and then A-flat major. The first pair shares E; the second shares C. Each is a descending-major-third relation between major triads. The scene's comic meaning is contextual, not part of the chord test.[^ref-70908b3474c9]
Relationships to Other Abstractions¶
Current abstraction Chromatic Mediant Domain-specific
Parents (1) — more general patterns this builds on
-
Chromatic Mediant is a kind of Relation Prime
A chromatic mediant is a binary relation on triads whose membership rule tests chord quality, third-related roots, and one shared pitch class.
Hierarchy path (1) — routes to 1 parentless root
- Chromatic Mediant → Relation
Neighborhood in Abstraction Space¶
Chromatic Mediant sits in a sparse region of the domain-specific corpus (94th percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.
Family — Musical Intervals & Voice Texture (9 abstractions)
Nearest neighbors
- Diminished Triad — 0.80
- All-Interval Tetrachord — 0.79
- Tertian — 0.79
- Pitch interval — 0.77
- Root (chord) — 0.77
Computed from structural-signature embeddings · 2026-10-17
Not to Be Confused With¶
- Relative mediant: a third-related pair with two common pitch classes under Kopp's classification, such as C major and E minor.[^ref-6cc8a6456404]
- Disjunct mediant: a third-related pair with no common pitch class under Kopp's classification. Lee uses a wider grouping for some of these.[ref-6cc8a6456404][ref-70908b3474c9]
- Chord Progression: an ordered succession of chords; chromatic mediant classifies a pair by a precise relation, even when discussed apart from a continuous progression.
- Pitch Interval: the live entry requires octave-specific pitches, whereas this test compares chord roots without fixing register.
- A modulation or fixed mood: neither follows from the chord relation alone.[^ref-70908b3474c9]
References¶
[^ref-6cc8a6456404]: David Kopp, Chromatic Transformations in Nineteenth-Century Music (Cambridge: Cambridge University Press, 2002), chap. 1, printed pp. 9–14, particularly pp. 9–11 and n. 17. Original book preview, 29 PDF pages, directly inspected; later chapters not consulted. https://api.pageplace.de/preview/DT0400.9780511057397_A23688676/preview-9780511057397_A23688676.pdf
[^ref-70908b3474c9]: Jason Yin Hei Lee, “The Semantic Evolution of Chromatic Mediants, A Baroque Origin of M8M Progressions” (original printed title uses a colon after “Mediants”), Music Theory Online 31, no. 2 (2025), Example 1 and [0.1], Example 9 and [2.4], [1.7], and n. 4. https://doi.org/10.30535/mto.31.2.6 . Original online article directly inspected; its embedded scores, Erik Heine's transcription, and Miles Goodman's underlying score were not independently inspected.