The strongest major key chord progression in Western music is the dominant V (or V7) to the tonic I.  We refer to this progression as an “authentic cadence” for the clear sense of resolution it provides a harmonic phrase, returning from the unstable dominant (V or V7) to the stable tonic (I).  A principal reason for this effect is the movement of the “leading tone” (also known as the major 7th) to the root.  Those familiar with solfège may recognize this as the pleasant resolution of “ti” to “do”.

While the ti/do resolution occurs naturally in the major key, the minor key does not have a major seventh degree.  To utilize the strong resolution of the V chord to the  minor tonic (i in this case), composers simply add the leading tone in authentic cadences.  This technique effectively raises the seventh degree of the minor scale, producing a scale known as “Harmonic Minor” due to its harmonic origins. 

The harmonic minor scale is very similar to the natural minor scale with one exception; the minor seventh of the natural minor scale is raised a half step to a major seventh.  The resulting increase in the gap between the sixth and seventh degrees and the decrease in the gap between the seventh degree and the root creates interesting effects both melodically and physically.  Guitarist may struggle initially with the three fret stretch between the sixth and seventh degree, but the stylistic and melodic options provided by the harmonic minor scale are well worth the effort.

Formula     W           H         W   W       H 1.5       W

A scale    A          B           C          D          E         F        G#          A

Interval    R         M2        m3        P4        P5      m6       M7*      P8