There are a number of different minor scales available, suiting different situations and chord progressions ... harmonic minor is better for playing over a perfect cadence, where chord V7 resolves ...

We’re sticking with C major - a nice keyboard key! When creating a harmonic progression ... reflecting a major or minor ...

All the chords built on other notes in the scale of C are minor ... added to a chord this is known as a seventh chord. The dominant seventh of a V chord can be shown by the symbol V7.