Minor Keys

There are three commonly recognized forms of the minor scale.  They are as follows:

Pure Minor
The scale built on the sixth scale degree of a major scale with no other altered notes besides the ones indicated in the key signature
     The relative minor of "C" major is "a" minor
     The pure "a" minor scale would be:  a-b-c-d-e-f-g-a

Harmonic Minor
The same basic scale as the pure minor, with one exception -- it's seventh scale degree is raised by one half step
     The harmonic form of the "a" minor scale would be:

Melodic Minor
It has the sixth and seventh scale degrees raised in its ascending form, but is the same as the pure minor in its descending form.
     The melodic form of the "a" minor scale would be:
          a-b-c-d-e-f#-g#-a (ascending)
          a-g-f-e-d-c-b-a    (descending)

It is advantageous to compare the minor scale forms with the parallel major scale.  This comparison shows the alterations of scale degrees that separate the major and minor modes.
Click here to see and hear all of the Minor Scales.