Composers will often merge two of these scales, natural minor and harmonic minor, for a more pleasing sound.
Recall the diatonic triads of both scales.
Notice that many of the triads are the same.
Three pairs of triads (III--III+, v--V, and VII--vii
o) are different due to harmonic minor's raised seventh degree.
III is prefered to III+. This is because III+, being an augmented chord, has a peculiar sound.
V is preferred to v since V contains a leading tone (and therefore is stronger). This does not mean that v cannot be used.
VII and vii
o are both used equally. As you will later learn, each has a different function.
The merged minor scale contains nine different diatonic triads.