Minor scale

A minor scale in musical theory is a diatonic scale whose third scale degree is an interval of a minor third above the tonic. While some definitions of minor scale encompass modes with the minor third, such as Dorian mode, most musicians use the term to refer to the natural minor, harmonic minor, and melodic minor scales described below. Also, compare major and minor.

Types of minor scales

A natural minor scale has the following interval pattern: tone semitone tone tone semitone tone tone

In equal temperament, this can be equated to

whole-step half-step whole-step whole-step half-step whole-step whole-step,

but in other meantone tunings the semitone is not half of a tone, but a somewhat larger interval.

If the scale is used with the corresponding key signature, the natural minor scale is written with no accidentals.

For example, in the key of A minor, the natural minor scale is:

A B C D E F G A'

Natural minor scale full octave ascending on a

Sometimes the natural minor scale is equated with the Aeolian mode, but a key characteristic of music in the minor mode in the common practice period of Western music is the use of the leading tone, a half step below the tonic. Music using the natural seventh degree, called the subtonic, sounds modal to Western ears; this music is commonly used in Peruvian and other ethnic music, and by modern Western composers such as Vaughan Williams who have a liking for this sound. But in music written from the 16th to 19th centuries, the chord built on the dominant (fifth scale degree) is almost always a major triad, at least at cadence points; consequently, the seventh degree of the scale must be raised with an accidental to make this possible. The next most important chord, the subdominant, is typically a minor triad.

These considerations of harmony lead to the harmonic minor scale, the same as the natural minor but with a chromatically raised seventh degree.

tone semitone tone tone semitone tone and a half semitone

For example, in the key of A minor, the harmonic minor scale is:

A B C D E F G♯ A'

A harmonic minor

The interval between the sixth and seventh degrees of this scale (in this case F and G sharp) is an augmented second. While some composers, notably Mozart, have used this interval to advantage in melodic composition, other composers have felt it to be an awkward leap, particularly in vocal music. Thus, for purposes of melody, either the subtonic is used, or the sixth scale degree is raised; either way, there is a whole step between these two scale degrees, considered more conducive to smooth melody writing.

Traditionally, music theorists have called these two options the ascending melodic (also known as heptatonia seconda, set form 7-34) and descending melodic minor scales:

A melodic minor ascending

A melodic minor descending

but historically, composers have not been consistent about using them in ascending and descending melodies. Just as often, composers choose one form or the other based on whether one of the two notes is part of the most recent chord (the prevailing harmony). Another reason might be the use of the mediant chord, based on the third degree of the scale, which is an augmented triad if the raised seventh degree is used; some composers prefer the use of the major triad and thus use the lowered seventh degree.

Finding key signatures

Minor modes use the same set of key signatures as major modes; whichever signature corresponds to the step pattern of the natural minor scale is considered the key signature for that minor mode. The major and minor keys which share the same signature are called relative; so C major is the relative major of A minor, and C minor is the relative minor of E-flat major.

The relative major is found by raising the minor tonic note by a tone and a semitone, which is three half-steps in equal temperament, and in any event an interval of a minor third. If you know that the key signature of G major has one sharp (see major scales for how to find this), then its relative minor, E minor, also has one sharp in its key signature.

This table illustrates the relative major key signatures for minor scales.|4♭|A♭ major|F minor

Major Scale|Minor Scale
C major|A minor
G major|E minor
D major|B minor
A major|F♯ minor
E major|C♯ minor
B/C♭ major|G♯/A♭ minor
F♯/G♭ major|D♯/E♭ minor
C♯/D♭ major|A♯/B♭ minor
E♭ major|C minor
B♭ major|G minor
F major|D minor

Additional note: it is possible to construct scales which cannot be written purely using a key signature, such as D-flat minor; double sharps/double flats can be written as accidentals, but not as part of a key signature. For example:

D♭ Minor Key Signature: B♭ + E♭ + A♭ + D♭ + G♭ + C♭ + F♭ + B♭♭ (the B♭ is now double flatted)

D♭ Natural Minor = D♭ E♭ F♭ G♭ A♭ B♭♭ C♭ D♭

D♭ Melodic Minor (Ascending + Descending) = D♭ E♭ F♭ G♭ A♭ B♭ C D♭ C♭ B♭♭ A♭ G♭ F♭ E♭ D♭

D♭ Harmonic Minor = D♭ E♭ F♭ G♭ A♭ B♭♭ C D♭

On rare occasions, short passages of music will be written in an enharmonic scale (in this case, C-sharp minor, which only has four sharps in its key signature, compared to the theoretical eight flats required for D-flat minor).

Circles of thirds

All three of the variant forms of the minor scale possess a complete circle of three major and four minor thirds in various arragements. If M is a major third and m a minor third, then starting from the tonic (eg A in A minor) we havemmMmmMM for the natural minor scale, mmMmMMm for the harmonic minor scale, andmmMMMmm for the ascending melodic minor. The major diatonic scale is simply a transposition of the natural minor scale, and the harmonic major scale is an inverted form of the harmonic minor scale, so all of these workhorse scales of the diatonic system possess such a circle of thirds. These circles only close in meantone tunings, since three major and four minor thirds exceed two octaves by 81/80, the syntonic comma, in just intonation.

Two major thirds in succession in such a circle gives an augmented triad, and two minor thirds a diminished triad. A major third followed by a minor third gives a major triad, and a minor third followed by a major third a minor triad. Hence all seven scale degrees have some variety of triad over that degree for all of these scales.

See also

*Major and minor
*Musical mode
*Diatonic functionality

Reference

*Gjerdingen, Robert O. (1990). "A Guide to the Terminology of German Harmony", Studies in the Origin of Harmonic Tonality by Dahlhaus, Carl, trans. Gjerdingen (1990).