Borrowing Across Keys
It’s quite common to use notes that do not exist within your original scale. It’s even common to switch to a new scale altogether.
First, we must ask ourselves why we would borrow from other keys in the first place. There are few reasons. One is that you might want to create pull towards a new chord. Another reason may be that you want to harmonize a melody that does not follow a scale exactly. Let’s start with the first example.
If you want to create pull to a new chord in your chord progression, and you don’t have a naturally-occurring Tritone for this, you can create one. Let’s do a chord progression in C major, and alter it from there.
How can we create more pull for the five chord?
One option is to create a Tritone that resolves to a few of that chord’s notes. To do that, we’ll need to add an extra note, in addition to altering an existing note. Below I have diagrammed each of these alterations. Notice the change in the Roman numeral from the original ii chord.
F# to C is a Tritone. This Tritone will resolve to a G and B. There is a half-step from F# to G, as well as from C to B. This artificial Tritone pulls us to our desired chord. We refer to this as a secondary dominant chord. Notice that D is the five of G. It is also the root of this altered chord. In light of this, the Roman numeral to the left should make more sense, the V7 of V.
This technique also sheds light on the origins of the harmonic minor scale from the second chapter.
By raising the 7th, you create the same tritone found in the major scale. The B natural in the V7 chord is our #7, found in the harmonic minor scale. Let’s examine:
Another way to borrow from other keys is to harmonize a melody that leaves key on its own accord.
Many reasons exist to do this, and I hope that you discover some. Mixing scales for fun can yield amazing results. All of these specific techniques, however, are beyond the scope of this book. Let’s do another example in C major. Our melody is circled in red.
Notice that I had to use a B♭ as well as the E♭. That is because B♭ belongs to the E♭ major scale. The quickest way to know this, of course, is to know the E♭ key signature! The chord E flat major is the flat three of C. Any accidental that comes before the Roman numeral will alter the root of that chord. Use the quality of the Roman numeral to figure out the rest of the notes in the chord. Capitalized being major, lower case being minor and all figured bass numbers being taken into account.
But what if you want to leave the key altogether? You can do this by creating an artificial Tritone, as we did earlier. Once you switch to the new chord, pretend its root is your new key. Since that has already been diagrammed, take a moment right now to try it. Another way to modulate, or move to a new tonal center, is to use what is called a pivot chord. In other words, use a chord that is common between two keys to switch from one key to another.
Another way to modulate, or move to a new tonal center, is to use what is called a pivot chord. In other words, use a chord that is common between two keys to switch from one key to another.
The E minor chord belongs to both C major and G major. In the diagram below, after the E minor chord appears, the rest of the grid will appear as G major. Also note that our G becomes the new one, or tonal center.
By using a common chord, we were able to switch between two scales. These were a few ways to borrow from other keys. Many more exist, but fall beyond the scope of this book. The tools presented in this book will provide you with the framework to understand the other methods that exist. It will also allow you to work though previously inaccessible texts on these methods.