Like the major scale, the minor scale has seven notes. However, it has three variations: natural minor, harmonic minor, and melodic minor. These variations differ in the way the sixth and seventh notes are altered.
In the natural minor scale, all the notes appear with the same accidentals as in the relative major scale. Hence the name natural minor:
Half steps are found between the II and III degree and between the V and VI (in red).
The seventh degree of a minor scale is often raised. The resulting scale is called a harmonic minor scale because the raising of the seventh degree is often harmonically motivated. Raising this note forms the dominant chord or dominant seventh chord on the fifth degree of the scale:
There is an augmented second between the VI and VII degree in this scale.
In addition to raising the seventh degree, the sixth degree can also be changed. The resulting scale is called the melodic minor scale. The main purpose of this accidental is to facilitate the melodic movement from the sixth degree to the seventh degree, avoiding the augmented second that is formed in the harmonic minor scale. This is why it is called the melodic minor scale:
In traditional music theory, the melodic minor scale is represented by the raised VI and VII degrees when the scale is ascending and descending without accidentals:
In real music, we can find the raised degrees ascending and descending.
See S > Scales for related entries