Closely related key
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In music, a closely related key is one sharing many common tones with the original key.
In elementary harmony, these are the family of keys that shares either all pitches or all but one pitch with the key it is being compared to. These keys are on either side of the original key on the circle of fifths and its relative majors or minors.
These keys, having 6 of 7 possible common tones with the original key, are the most commonly used destinations or transpositions in a modulation, because these keys are the most closely related, are based on the subdominant and dominant of the home key, which are often structurally significant, and which, with the tonic, create the strongest of tonal chord progressions.
| Major | Relative Minor | Dominant and Subdominants |
|---|---|---|
| C | a | F, G, d, e |
| G | e | C, D, a, b |
| D | b | G, A, e, f# |
| A | f# | D, E, b, c# |
| E | c# | A, B, f#, g# |
| B | g# | E, F#, c#, d# |
| Gb (F#) | eb (d#) | Cb (B), Db (C#), ab (g#), bb (a#) |
| Db | bb | Gb, Ab, eb, f |
| Ab | f | Db, Eb, bb, c |
| Eb | c | Ab, Bb, f, g |
| Bb | g | Eb, F, c, d |
| F | d | Bb, C, g, a |
In modern music, the closeness of a relation between any two keys 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.
See also: Pitch space.
References
- Howard Hanson, Harmonic Materials of Modern Music. Appleton-Century-Crofts, Inc, 1960.