Harmonic minor keys are used when writing chords ... the dominant seventh was often substituted with an augmented chord.This gave the tonic-dominant a new and modern feel. This can be heard ...

When working in a major key, chords or triads are based upon different degrees of the scale, reflecting a major or minor tonality at the individual chord level. Chords I, IV & V are all major ...

All the chords built on other notes in the scale of C are minor, except chord VII - the notes B – D – F, which is diminished. When a seventh is added to a chord this is known as a seventh chord.