3.19Compare major and minor directly

Play:

C major

C → F → G7 → C

I → IV → V7 → I

Then:

C minor

Cm → Fm → G7 → Cm

i → iv → V7 → i

Notice that G7 is the same dominant chord in both:

G B D F

Why does G7 work in C minor?

Because B natural is the raised 7th of C harmonic minor.

C natural minor has B♭.

C harmonic minor raises:

B♭ → B

to create:

B → C

leading-tone resolution.