what is a key? part vi

In this post we're going to look at some examples of chord borrowing. By this is meant that a chord is taken from another, often parallel, key. For an example let's look at the opening to the Finale (3rd movement) of Giuliani's Guitar Sonata, op. 15:

This piece is in C major. The not-too-subtle arrows, however, are pointing out a chord (the same chord, thrice) which contains an Ab, patently not a card carrying member of the C major scale. The chord in question is a B diminished seventh chord (minus the third, a D) over a pedal note C. This fully diminished chord is the VII chord of the C harmonic minor scale.

If we (or rather, Giuliani) had stuck only with the VII of C major we (he) would have had a B half-diminished chord. Both of these VII chords (can) resolve the same way: to the I chord. However -- and just from a bare bones technical point of view, minus any emotion or drama imparted to the music -- the fully diminished chord, because of the Ab, feels even more in need of resolving. So even though this chord is not part of C major, it still causes motion towards the C major triad.

This happens fairly often with the IV chord. In a major key the IV (which is a major chord) is followed/replaced by the IV from the parallel harmonic minor, which IV chord is a minor triad.


Cmaj | Fmaj  Fmin | Cmaj |


The first time I really remember hearing this kind of borrowing was in the Beatles' Across the Universe, where there is a Gmin to Dmaj. It pops out but leaves no doubt as to where it's going.

On a related note is the Picardy Third (click here for the Wikipedia entry). This is a fairly old harmonic practice that uses a major triad instead of an expected minor one at the end of pieces, etc, in minor/modal keys.