Chords of minor keys
This article, chords of minor keys, is intended as a sequel to my previous two-part article: Chords of Major Keys. That article covers its topic in detail, explaining how music in any major key can be harmonised using notes of the major scale belonging to that key. It explains how the chords most commonly used in major key music are formed by taking combinations of those scale notes separated by intervals of thirds. This applies equally to chords of minor keys. The notes of minor scales can be combined in exactly the same way to reveal the chords most commonly encountered in minor key music. If you're not clear about what "separated by intervals of thirds" means, then you should read that article before reading this one.
Chords of Major Keys
Music written in a minor key means music that has been composed primarily by using notes of a minor scale arranged in such a way that, apart from being musically pleasing, the first scale note (called the tonic) is felt as the most important note in the music - the one that feels like 'home' when we hear it. Combinations of these notes separated by intervals of thirds produce the chords that belong to that key; that is, chords that we'll most often encounter when playing music in a minor key, or that will be our most common choices when writing music in a minor key.
The minor scale has three recognised forms: the original natural (or pure) minor scale plus two modified forms of it, known as the harmonic minor and melodic minor scales.
If you want to learn more about how the various forms of the minor scale came about, please visit my article: The Minor Scale
For our purposes we just need to show the three forms. To do this we'll use the three forms of the minor scale that belong to the key of A minor
- Natural minor: A B C D E F G A
- Harmonic minor A B C D E F G# A
- Melodic minor: A B C D E F# G# A
Note* The melodic minor scale has a descending form that differs from the ascending form. The descending form is exactly the same as the natural form of the scale (in reverse) so can be ignored for our purposes.
Combining the scales gives us a note source of nine notes:
A B C D E F/F# G/G#
There are still seven scale degrees, but the 6th and 7th scale degrees are variable.
By combining the notes in 3rds, exactly as we did with the major scale, we have sets of chords belonging to the key of A minor.
Keep in mind that while its convenient to say that these chords come from the scale, it's not strictly accurate. It would be more correct to say that they agree with the notes of the scale. Chords came into existence as a result of separate melodies combining, and developed through composers building chords according to the sound they wanted. Their habit of raising the 7th scale note of the natural minor by a semitone, because it made for stronger chord progressions, is what led theorists to make a new form of the scale, which they called 'harmonic minor'.
The table below shows two sets of chords that are obtained by combining notes (separated by 3rds). Combining three notes in this way gives us a set of triads and combining four notes gives us a set of seventh chords.
Note* The convention of using UPPERCASE Roman numerals to specify major and augmented chords, plus lowercase Roman numerals for diminished and minor chords applies to minor keys as well as to major keys.
Chords of minor keys - Example key: A minor
Note. A different convention names chord VII as bVII, to show that its root is a semitone lower than vii, the chord built on the raised 7th scale degree.
The tonal functions of chords in minor keys are more or less similar to their functions in major keys but with some differences:
Chord i (tonic minor) has the same restful, stable and final feeling as the tonic major chord has in major keys.
Chord ii (supertonic diminished) is dissonant, and is classed as subdominant or pre-dominant in function, meaning it is most commonly followed by the dominant chord, V or V7. Where voice leading is important, the chord is played in first inversion. Where voice leading doesn't matter, such as in strummed guitar chords, for example, the inversion isn't important, but it's almost always embellished or extended and played as a diminished 7th or half diminished 7th chord (also called minor 7thb5).
Because this is exactly the same chord as chord vii in the relative major key, it can also have an expectation to resolve up a semitone to chord III in exactly the same way that chord vii (the same chord) resolves up a semitone to the tonic chord. Careless use of this chord in compositions employing functional harmony, can cause an apparent shift of tonal centre. In other words, (in our example key of A minor) chord ii (B diminished) has an expectation to resolve up to C major in such a way that it can cause listeners to hear C major as a new tonic chord. Effectively, we'll have unintentionally changed key (modulated) to the key of C major. Chord ii also has a minor form too as the chart above shows (B minor), but it's not so common.
Chord III (mediant major) is commonly used, but chord III+ (mediant augmented) corresponding with the harmonic minor scale is rarely used.
Chord iv (subdominant minor) is far more common than chord IV (subdominant major). The major chord's notes agree with the melodic minor scale in this case. The purpose of this scale, as its name suggests, was melodic rather than harmonic, so, although a few chords can be formed from it that aren't available from the other two scales, they tend not to be very common or useful.
Both forms of the subdominant chord in minor keys have a pre-dominant function. That is, they lead smoothly to chord V (the dominant). Note, however, that, if we add a 7th to the major version (D7), it no longer has a convincing 'pre-dominant' quality, It has more of a secondary dominant quality, i.e., it sounds like the dominant chord of a different key.
Example: Key A minor. Chord IV7 is D7, which is the dominant 7th of G major and G minor.
Chord v (dominant minor) has a weak dominant function but chord V (dominant major), which corresponds with the harmonic minor scale, has a much stronger dominant function and is the reason that the harmonic minor scale was invented in the first place. The four note dominant 7th chord has an even stronger function, due to containing a dissonance that returning to the tonic resolves in a musically satisfying way.
Note - The dominant can be considered as the opposite of the tonic. Whereas the tonic is stable restful and 'at home', the dominant is unstable, active and "far from home but poised to return".
Chord VI (submediant major) is far more common than chord (#)vi (raised submediant diminished).
Chord VII (subtonic major) is common in pop and rock music, whereas chord vii (leading note diminished) is more common in classical and jazz.
You can combine more than four notes and, as with major keys, obtain sets of 9th, 11th and 13th chords (five, six and seven notes respectively).
If you need help understanding the naming of chords that result from combining notes, you can learn about it in my Chord Building article.
As is the case with major keys, we can often find chords in minor keys borrowed from other sources. My article, Chords of major keys - part 2 covers this in more detail. The principles apply equally to minor keys, so have a look at that article if you'd like more information on the most common out of key chords found in key based music (i.e., most Western music).
That concludes the article on understanding the common chord choices for music composed in minor keys. Minor keys are a bit more flexible than major keys, and if you want to compose in a minor key, you can experiment with other chord choices too for interesting, if unconventional, musical effects.