The harmonic minor scale is also commonplace in classical ... which is where this scale really shows its purpose. An F note (the b5) is the target choice for the Bm7b5. All these note choices ...

But if you still find yourself trapped in the confines of pentatonic and major scales, a good way to break this harmonic stalemate ... around the chords of A minor and F Major, extended to ...

Harmonic minor keys are used when writing chords. There is another version of the minor key known as the melodic minor. This is used when writing a melody. Each key signature has two possible keys.