Every major key has a darker partner: the minor key on the same note. Borrowing one chord from it gives a song a moment of colour without leaving home.
- ♭VII (B♭ in C): bold, rock-anthem — try B♭ – F – C at the end of a chorus.
- iv (Fm in C): bittersweet — play F, then Fm, then C.
- ♭VI (A♭ in C): dramatic, cinematic.
- ♭III (E♭ in C): bright and unexpected.