You probably already know that there are more than one of them; it actually has three different forms:
– Aeolian, which is the natural minor scale
– Harmonic and
Let’s see what wonderful things you can do with all three of them. We will follow musical history, and therefore we start with Minor Aeolian.
The Aeolian scale
A minor Aeolian is the so called parallel of C major, which means that in this scale exactly the same notes are used as in C major (only the white keys on the piano), and therefore exactly the same chords. But they have other functions within the overall harmony, as you can see in the following picture. In minor, like in major, the tonic, subdominant and dominant chords are the primary chords. In the picture they are accentuated by drawing a nice rectangle around them. And the dim-chord (B-) is accentuated in red.
Now we can see that major and minor are a sort of mirror-images of each other. In C major the major triads (C, F and G) are the primary chords, and the three minor triads (Dm, Em and Am) are secondary chords. In A minor it is exactly the other way around: the minor triads are the primary chords and the major triads are the secondary chords. This means that in A minor the minor triads bear the main functionality, while the major triads are the mediants. (There is also another nice symmetry. The B- triad in C major is the second chord from the right (VII-), while in A minor it is the second chord from the left (II-). This has no musical significance but we still wanted you to see it.)
So. Again we are going to play around with the same seven chords. But because of the fact that in the minor scale they have other functions the result will be quit different.
The Harmonic scale
Next let´s look at the alterated minor scales. In the minor Aeolian scale there is no leading note, and therefore the change Vm – Im is not as strong as V – I. To make the ending more defined (just like in the major key), the logical thing to do was to change the Vm into V (and Vm7 into V7 of course).
The Melodic scale
The harmonic scale has in it an augmented second (flat sixth to sharp seventh, F to G# in A minor harmonic) which is quite difficult to sing and was traditionally considered unmelodic and forbidden. To overcome this problem also the sixth was sharpened. Raising the sixth also gives us the possibility to change the diminished II- into a minor triad.
Minor in Major
As we saw earlier, major and minor are mirror-images of each other. In the harmonic and melodic scale minor was altered to sound more like major by raising of the sixth and the seventh degree. In the same way major can be altered to sound more like minor (Aeolian), by flattening of the sixth and seventh note.
Lowering the seventh gives the possibility to change the diminished VII- into a major triad. So, again we see a nice symmetry between major and minor. In minor melodic all chords except Im and IIm are major triads, and in the major-minor scale all chords except I and VII are minor triads.