MINOR SCALE

Although there is only one major scale the minor scale has three distinct forms.  Theses are:

Natural Minor
Harmonic Minor
Melodic Minor 

All of the minor scales share a dramatic, sometimes melancholy feel which is well suited to darker, more brooding styles of music.  They are particularly frequently used in most forms of metal.  The minor scales are also closely related to the Blues scale.

Natural minor is the minor scale directly related to the major scale and therefore the modes.  Aeolian to the major scale’s Ionian.

Harmonic Minor is often used in classical music and is identical to the natural minor scale except for the 7th which is a semitone higher.

Melodic minor is a little more complicated.  In its ascending form it resembles a cross between the major and natural minor scale while when descending it should be played as the natural minor scale.  This may be a little confusing but in standard western music theory it is the accepted way of playing the melodic minor scale.