Melodic minor scales are similiar as a natural minor scales except that while ascending the sixth and the seventh degrees are both raised by half steps. But while descending it is basically same as the natural minor scale.
So we turn the sixth and seventh degrees to their original state while descending. While ascending melodic minor scales follow this pattern of whole steps and half steps between their notes:
On higher or lower octaves this pattern repeats while ascending. The pattern of descending melodic minor scale is same as the descending natural minor scale. There are several ways to build a melodic minor scale. The easiest way is just raising the sixth and seventh degrees of the relevant natural minor scale. Let’s see an example.
A Melodic Minor Scale
This is A natural minor scale both ascending and descending. Now, let’s raise the sixth and the seventh degrees by half steps while ascending and turn them back to their former state while descending.
Notice how we placed sharps to F and G while ascending and how we placed naturals to the same notes while descending.
Building Melodic Minor Scales with Tetrachords
While ascending, all harmonic scales have minor tetrachords (with Whole-Half-Whole step pattern) as lower tetrachords and major tetrachords (with Whole-Whole-Half step pattern) with whole steps between them. If we start with any note and maintain this pattern, we can build a melodic minor scale in no time. Let’s see an example.
So this is F minor tetrachord which is the lower tetrachord of ascending F melodic minor scale. Now, we should build the upper tetrachord of this scale. It starts with C and then three more notes, D, E and F come.
When we combine these two tetrachords with a whole step as a link, we can build ascending F melodic minor scale.
As I mentioned before, descending melodic minor scale is same as descending natural minor scale. So it looks like the following.
As you can notice, the sixth and the seventh degrees of ascending F melodic minor scale turns back to F natural minor scale while descending. Now let’s have a look at all melodic minor scales with their key signatures both ascending and descending.