Today while teaching my Jazz Theory & Aural Skills class at DU, I had a revelation – a way of explaining the notion of “secondary dominant” chords by appealing to concepts and terminology from the TV show “Downton Abbey” (or substitute your favorite show, movie, or book about British aristocracy). Sound far-fetched? Read on.
As many musicians know, “most” chords in “most” songs are diatonic, meaning they consist exclusively of notes that are in the key. So in the key of C, we expect to see C, Dmi, Emi, F, G, Ami, and Bdim chords as triads, or Cma7, Dmi7, Emi7, Fma7, G7, Ami7, and Bmi7b5 as seventh chords, since these chords consist of notes from the key of C. We often label these chords with Roman numerals: I, ii, iii, IV, V, vi, and viiø. But most songs also include at least a few chords that are not diatonic – chords that include at least one note not in the key. The majortiy of these non-diatnoic chords fall into a few basic categories that explain the function of the chord, and by far the most important such category is the “secondary dominant”.
OK, I know, I promised you Downton Abbey, and so far, the hasn’t been an earl in sight. Well, here’s the deal. The most important relationship in music is V-I. That is, the most important chord in music is the I chord (called the “tonic”), and the V chord (called the “dominant”) serves to lead to the I chord. We could even say that the I chord is so important – wait for it – so important that it gets its own personal valet, the V chord. V for valet (pronounced, in Britain, to rhyme with “palette”), get it?
In the key of C, this is to say that G7 typically leads to Cma7. But sometimes, other chords like to feel important too. Sometimes, for instance, the ii chord – Dmi7 – wants to feel important. How do we make that happen? We give him his own personal valet too, of course! That is, we give him his own personal V chord. In the key of D minor, the V chord would be A7. We could say that A7 is the valet of Dmi7. Or, in Roman numeral terms, we could say it is the V of ii. In traditional classical notation, that is written V/ii, read as “V of ii”.
We’re still in the key of C, so Cma7 – the I chord – is still the earl of the estate. And G7 is still the primary valet – the personal valet of the I chord. But A7 chords do often occur as the personal valets of the ii chord, Dmi7. Chords like A7 – not the primary valet (the actual V chord in the key), but valets of some other diatonic chord – might be called secondary valets. The valets of ii, and of iii, and of IV, and of V, and of vi, are all common chords. So in the key of C, we may see A7 chords that lead to Dmi7 (V/ii leading to ii), B7 chords leading to Emi (V/iii leading to iii), C7 chords leading to Fma7 (V/IV leading to IV), D7 chords leading to G7 (V/V leading to V), or E7 chords leading to Ami7 (V/vi leading to vi).
These are the most common non-diatonic chords there are. And these chords that I am calling secondary valets in reference to Downton Abbey are, of course, actually called “secondary dominants”. Dominant = V, and V is for valet. So there you have it!
Some day, I’ll explain how a “suspension” can be explained using the Wile E. Coyote and The Road Runner cartoons.