Music Theory: Chords of Minor Keys
Music in Minor Keys
Music 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 scale notes separated by intervals of thirds (e.g. A C & E or D, F & A, etc) 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 chords 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.
Here are the three forms of the minor scale that belong to the key of A minor
- A Natural minor: A B C D E F G A
- A Harmonic minor A B C D E F G# A
- 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.
Using all the scales' notes 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, (i.e., taking alternate scale notes), 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 chords used when composing music in minor (or major) keys are chosen not just chosen for their harmonious sound but also for their ability to affect the key. These abilities are their so-called tonal functions. 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)
The HOME chord - This has a similar restful, stable and final feeling as the tonic major chord has in songs in major keys.
Chord ii (Supertonic Diminished)
This chord is dissonant, and is classed as pre-dominant in function, meaning it's most commonly followed by the dominant chord, V or V7. Where voice leading is important, the chord is normally 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 7b5). As this is exactly the same chord as chord vii in the relative major key, its root can resolve up a semitone to chord III in exactly the same way that chord vii's root (the same chord) resolves up a semitone to the tonic chord. Chord ii also has a minor form as the chart above shows (B minor), but it's not so useful.
Chord III (Mediant Major)
This chord is commonly used, but chord III+ (mediant augmented) corresponding with the harmonic minor scale is rarely used.
Chord iv (Subdominant Minor)
Chord iv 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.
Chord v & V (Dominant Minor and Major)
The dominant chord's function is to lead back to the TONIC or home chord. Chord v, the dominant minor has a weak function but chord V (dominant major), which corresponds with the harmonic minor scale, has a much stronger function due to it containing a leading note to the key's tonic. That's the reason 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". That's the dominant effect.
Chord VI (Submediant Major)
Chord VI, the submediant major, starting on the 6th naturally occurring scale, note is far more common and functional than chord (#)vi (raised submediant diminished) starting on the raised 6th. As the raised 6th agrees only with the melodic form of the minor scale, it has very limited, if any, harmonic (chordal) use in minor keys.
Chord VII (Subtonic Major)
Chord VII (starting on the naturally occurring 7th degree) is common in pop and rock music, whereas chord vii, the leading note diminished (starting on the raised 7th degree) is more common in classical and jazz. As mentioned above, an alternative convention names chord VII as bVII (flat 7), to show that its root is a semitone lower than vii, the chord built on the raised 7th scale degree.
The above covers all the possible triads (3-note chords separated by thirds) plus 4-note 7th chords that you can construct using the notes of any minor key's scales. You can also combine more than four notes and, as with major keys, obtain sets of 9th, 11th and 13th chords (five, six and seven notes respectively).
© 2011 chasmac