Borrowed Chords

A secondary dominant borrows a chord in order to point at another chord. The other way to leave a key is to borrow simply for the colour, with no pointing involved — and the place songs borrow from is nearly always the parallel minor.

Parallel, here, means the minor key with the same root. C major and C minor are parallel; C major and A minor are relative, which is a different relationship. The parallel minor of a key shares its root but has three notes flattened, the third, sixth and seventh, and so it contains chords the major key does not.

From C minor you can lift E flat major, A flat major, B flat major and F minor, and drop any of them into a song in C major. They are written ♭III, ♭VI, ♭VII and iv.

The ♭VII is the one rock uses most, and it is worth noticing that we have now met it twice for two different reasons — in the last lesson it arrived as part of Mixolydian, and here it arrives as a chord borrowed from the parallel minor. Both explanations describe the same chord. Which one you use depends on whether the flattened seventh is running through the whole song or is a one-off colour.

This track is in A major, and its chords include both C major and G major. Neither belongs to A major — the key has C sharp and G sharp — but both belong to A minor. They are ♭III and ♭VII, and together they are the single most recognisable sound in classic rock.

C

C major, the ♭III in the key of A.

G

G major, the ♭VII in the key of A.

A rock jam in A major whose chord list includes A, D, E and A7 from the key, plus C and G borrowed from A minor.

The other borrowing worth knowing on its own is the minor four. In a major key the IV chord is major; swapping it for a minor one, borrowed from the parallel minor, produces a particular ache that pop and soul writers have relied on for seventy years. It very often appears immediately after the major IV, so you hear the same chord twice, brightened then darkened.

This pop track is in G major. The IV chord is C major, and a C minor also turns up.

Cm

C minor in the key of G — the minor four, borrowed from G minor.

A pop groove in G. Most of its chords come straight out of the key, with a C minor among them.