Closely related key
In music, a closely related key is one sharing many common tones with an original key, as opposed to a distantly related key (or "close key" and "distant key"). In music harmony, such a key shares all, or all except one, pitches with a key with which it is being compared, and is adjacent to it on the circle of fifths and its relative major or minor.
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 or C to C minor to E♭ major. For example, "One principle that every composer of Haydn's day [Classical music era] 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 (Mozart), K. 309, modulates only to closely related keys (the dominant, supertonic, and submediant).
Given a major key tonic (I), the related keys are:
- vi (submediant or relative minor): same key signature
- IV (subdominant): one less sharp (or one more flat) around circle of fifths
- V (dominant): one more sharp (or one fewer flat) around circle of fifths
- i (parallel minor): same tonic, different key signature
- ii (supertonic, the relative minor of the subdominant)
- iii (mediant, the relative minor of the dominant)
Major Relative minor Subdominant, dominant,
and their relatives
Parallel minor C Am F, G, Dm, Em Cm G Em C, D, Am, Bm Gm D Bm G, A, Em, F♯m Dm A F♯m D, E, Bm, C♯m Am E C♯m A, B, F♯m, G♯m Em B G♯m E, F♯, C♯m, D♯m Bm G♭ E♭m C♭, D♭, A♭m, B♭m F♯m D♭ B♭m G♭, A♭, E♭m, Fm C♯m A♭ Fm D♭, E♭, B♭m, Cm G♯m E♭ Cm A♭, B♭, Fm, Gm E♭m B♭ Gm E♭, F, Cm, Dm B♭m F Dm B♭, C, Gm, Am Fm
Starting from a minor key (i), the closely related keys are the subdominant minor (iv), the dominant minor (v), the relative major (♭III), and the relative majors of the subdominant and dominant (♭VI and ♭VII).
Another view of closely related is that there are six closely related keys, based on the tonic and the remaining triads of the diatonic scale, excluding the dissonant leading-tone diminished triad. Four of which differ by one accidental, one with the same key signature, and the parallel modal form. In the key of C major these would be: D minor, E minor, F major, G major, A minor, and C minor.
In modern music, the closeness of a relation between any two keys or sets of pitches may be determined by the number of tones they share in common, which allows one to consider modulations not occurring in standard major-minor tonality. For example, in music based on the pentatonic scale containing pitches C, D, E, G, and A, modulating a fifth higher gives the collection of pitches G, A, B, D, and E, having four of five tones in common. However, modulating up a tritone would produce F♯, G♯, A♯, C♯, D♯, which shares no common tones with the original scale. Thus the scale a fifth higher is very closely related, while the scale a tritone higher is not. Other modulations may be placed in order from closest to most distant depending upon the number of common tones.
Another view in modern music, notably in Bartók, a common tonic produces closely related keys, the other scales being the six other modes. This usage can be found in several of the Mikrokosmos piano pieces.
When modulation causes the new key to traverse the bottom of the circle of fifths this may give rise to a theoretical key, containing eight (or more) sharps or flats in its notated key signature; in such a case, notational conventions require recasting the new section in its enharmonically equivalent key.
- Schonbrun, Marc (2006). The Everything Music Theory Book, p.76. ISBN 1-59337-652-9.
- George T. Jones (1994). HarperCollins College Outline Music Theory, p.217. ISBN 0-06-467168-2.
- Ulrich, Homer (1966). Chamber Music, p.175. ISBN 978-0-231-08617-2.
- Benward & Saker (2009). Music in Theory and Practice: Volume II, p.155. Eighth Edition. ISBN 978-0-07-310188-0.
- Barry, Barbara R. (2000). The Philosopher's Stone: Essays in the Transformation of Musical Structure, p.19. ISBN 1-57647-010-5.
- Benward & Saker (2003). Music: In Theory and Practice, Vol. I, p.243. 7th edition. McGraw-Hill. ISBN 978-0-07-294262-0. "Most modulations occur between closely related keys, which are those keys that differ by no more than one accidental in the key signature."
- Jones (1994), p.35-36.
- Howard Hanson, Harmonic Materials of Modern Music. Appleton-Century-Crofts, Inc, 1960.