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:

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

or

tone semitone tone tone semitone tone tone

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'

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 prefer this sound. But in music written from the 16th to 19th centuries, the chord built on the dominant (fifth scale degree) is 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.

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

A  B  C  D  E  F  G# A'

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 felt it to be an awkward leap. 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 and descending melodic minor scales:

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 3 semitones (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.

Additional note: it is possible to construct minor scales which do not correspond to a key signature, such as D-flat minor. On rare occasions short passages of music will be in such keys, so these additional scales have some use; but for purposes of practice, an enharmonic scale (in this case, C-sharp minor) can be used.

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).