There are other scales, such as the Dorian mode (1-2-b3-4-5-6-b7), but the minor pentatonic and natural minor are the ones we usually learn first. By contrast, the harmonic minor has a unique ...

Harmonic minor keys ... This is known as the relative minor. So G major, for example has a key signature of one sharp, but this is also the key signature for E minor. To find this, just count ...