thumb|right|upright=1.4|[[Circle of fifths showing major and minor keys.]]
In music, a closely related key (or close key) is one sharing many common tones with an original key, as opposed to a distantly related key (or distant key). In music harmony, there are six of them: four of them share all the pitches except one with a key with which it is being compared, one of them shares all the pitches, and one shares the same tonic.
Such keys are the most commonly used destinations or transpositions in a modulation, because of their strong structural links with the home key. Distant keys may be reached sequentially through closely related keys by chain modulation, for example, C to G to D. For example, "One principle that every composer of Haydn's day <nowiki>[</nowiki>Classical music era<nowiki>]</nowiki> kept in mind was over-all unity of tonality. No piece dared wander too far from its tonic key, and no piece in a four-movement form dared to present a tonality not closely related to the key of the whole series." For example, the first movement of Mozart's Piano Sonata No. 7, K. 309, modulates only to closely related keys (the dominant, supertonic, and submediant).
Given a major key tonic (I), the related keys are:
- ii (supertonic,): different tonic, same key signature
- i (parallel minor): same tonic, different key signature
alt=|center|thumb|upright=1.8|Closely related keys in C.
Specifically:
{| class="wikitable"
!Original key (major)
!Submediant (relative minor)
!Subdominant, dominant, supertonic, and mediant
!Subdominants
!Dominants
!Parallel minor
|-
|C
|Am
|F, G, Dm, Em
|B, E, A, D
|D, A, E, B
|Cm
|-
|G
|Em
|C, D, Am, Bm
|F, B, E, A
|A, E, B, F
|Gm
|-
|D/E
|Bm/Cm
|G/A, A/B, Em/Fm, Fm/Gm
|C/D, F/G, B/C, E/F
|E/F, B/C, F/G, C/D
|Dm/Em
|-
|A/B
|Fm/Gm
|D/E, E/F, Bm/Cm, Cm/Dm
|G/A, C/D, F/G, B/C
|B/C, F/G, C/D, G/A
|Am/Bm
|-
|E/F
|Cm/Dm
|A/B, B/C, Fm/Gm, Gm/Am
|D/E, G/A, C/D, F/G
|F/G, C/D, G/A, D/E
|Em/Fm
|-
|B/C
|Gm/Am
|E/F, F/G, Cm/Dm, Dm/Em
|A/B, D/E, G/A, C/D
|C/D, G/A, D/E, A/B
|Bm/Cm
|-
|F/G
|Dm/Em
|B/C, C/D, Gm/Am, Am/Bm
|E/F, A/B, D/E, G/A
|G/A, D/E, A/B, E/F
|Fm/Gm
|-
|C/D
|Am/Bm
|F/G, G/A, Dm/Em, Em/Fm
|B/C, E/F, A/B, D/E
|D/E, A/B, E/F, B/C
|Cm/Dm
|-
|G/A
|Em/Fm
|C/D, D/E, Am/Bm, Bm/Cm
|F/G, B/C, E/F, A/B
|A/B, E/F, B/C, F/G
|Gm/Am
|-
|D/E
|Bm/Cm
|G/A, A/B, Em/Fm, Fm/Gm
|C/D, F/G, B/C, E/F
|E/F, B/C, F/G, C/D
|Dm/Em
|-
|A/B
|Fm/Gm
|D/E, E/F, Bm/Cm, Cm/Dm
|G/A, C/D, F/G, B/C
|B/C, F/G, C/D, G/A
|Am/Bm
|-
|F
|Dm
|B, C, Gm, Am
|E, A, D, G
|G, D, A, E
|Fm
|-
|}
In a minor key, the closely related keys are the parallel major, mediant or relative major, the subdominant, the minor dominant, the submediant, and the subtonic. In the key of A minor, when we translate them to keys, we get:
- A major (I)
- C major (III)
- D minor (iv)
- E minor (v)
- F major (VI)
- G major (VII)
Another view of closely related keys is that there are six closely related keys, based on the tonic and the remaining triads of the diatonic scale, excluding the dissonant diminished triads.
See also
- Chromatic mediant
- Common chord (music)
- Monotonality
- Parallel and counter parallel
- Pitch space