All scales are determined by the intervals from note to note.  For example, a minor scale has half steps between 2 - 3 and 5- 6.

The following example shows a basic A minor scale.

W = Whole step

H = Half step

Remember - a tetrachord is a four note scale pattern.  Two tetrachords combined make a scale.  In a minor scale, only the lower tetrachord is the same.

Lower Tetrachord

1 - W - 2 - H - 3 - W - 4

Upper Tetrachord

5 - H - 6 - W - 7 - W - 8

Together

1 - W - 2 - H - 3 - W - 4 - W - 5 - H - 6 - W - 7 - W - 8

With minor scales there are also variations.  They are:

Harmonic Minor
Melodic Minor (Ascending)
Melodic Minor (Descending)

The following are the tetrachords:

Harmonic Minor

Lower Tetrachord

1 - W - 2 - H - 3 - W - 4

Upper Tetrachord

5 - H - 6 - W/H - 7 - H - 8

Together

1 - W - 2 - H - 3 - W - 4 - W - 5 - H - 6 - W/H - 7 - H - 8

Melodic Minor (Ascending)

Lower Tetrachord

1 - W - 2 - H - 3 - W - 4

Upper Tetrachord

5 - W - 6 - W - 7 - H - 8

Together

1 - W - 2 - H - 3 - W - 4 - W - 5 - W - 6 - W - 7 - H - 8

Melodic Minor (Descending)

Lower Tetrachord

8 - W - 7 - W - 6 - H - 5

Upper Tetrachord

4 - W - 3 - H - 2 - W -1

Together

8 - W - 7 - W - 6 - H - 5 - W - 4 - W - 3 - H - 2 - W - 1