Part IV - Chapter 4
"Chords - Modulation"
Hey all! The Ultimate Guide to Guitar has arrived at the last stretch of theory it has to offer! Chord progressions is where we left off, and we'll continue there this week... After that, there's only one more technique article left, and we'll have reached the end of our wondrous journey through the vastness of guitar theory and practice!
We still have some ground to cover before we get there, though. Today, we'll be assessing a very important aspect of chord progressions that we have not yet discussed: modulation of chord progressions, which means the shifting of a progression's key. Modulating progressions, both modal and tonal ones, can make them sound a lot more interesting and varied, but it's not possible to modulate to any random key or mode at any random point in a progression. Modulating isn't always easy: a valid and good-sounding modulation is pretty difficult to achieve.
However, there are multiple ways to achieve modulation of a chord progression in a correct way. Of all these methods, we'll discuss the most basic and most commonly used ones: common chord modulation (using a "pivot chord" that is present in both the old and the new key), common tone modulation (using a "pivot pitch" in the melody present in both the old and new key), and direct modulation (or "phrase modulation", which means jumping between closely related keys)! This article will describe these common methods of modulation in chord progressions, with short tabbed examples of modulated progressions so that you can see the various methods of modulation being applied in practice!
Before we can start looking into these methods of modulation, though, we need to learn about related keys... You can't just shift from one key to another at random; some keys are not really compatible, while other keys are considered "closely related", making it possible to shift between them. But which keys are related to which? And how does this apply to modal music? We'll be looking into this in the first section of this article.
Today's table of contents looks like this:
1. Related and parallel keys: how do we know which keys are interchangable?
2. Common chord modulation: changing keys using a chord that belongs to both the original and the new key!
3. Common tone modulation: similar to common chord modulation, but using a common pitch instead of a common chord!
4. Direct modulation: shifting to a related key between phrases!
The last chapter of theory in the Ultimate Guide to Guitar awaits you... let's go!
Related And Parallel Keys
Before we start learning how exactly the process of modulation works, we need to consider that modulation doesn't work between just any two keys... to modulate succesfully between two keys, the original and the new key need to be related. There needs to be similarity between them, in order to be able to make a smooth transition... But what similarity am I talking about? What exactly makes two keys "related"? Well, the two possibilities are:
The two keys share a number of notes (related keys)
The two keys share their tonal centre (parallel keys)
Let's look into these two possible relationships between keys, and how modulation works with these different relationships!
A. Related Keys
The first possible relationship between keys that we're going to look into, is between keys that share a number of notes. If a key has notes in common with another key, the keys are considered "related"; and more importantly, the more notes the keys have in common, the more closely related they are! There are specific names for the relative distance of two keys' relationship:
If two keys have 6 or more notes in common, they're called "closely related keys".
If two keys share less than 6 notes, these keys are referred to as "distantly related keys".
Now, if we have a music piece or a progression in a certain key, how do we know which keys it's closely related to, and which it's distantly related to? Finding that out is pretty easy! Remember the Circle of Fifths? We learned about it in Chapter II-1
. Check that lesson out if you don't remember exactly how the Circle of Fifths works! In any case, keep the picture of the Circle of Fifths
from that lesson close, since we're going to learn how to use it to find out a key's closely related keys... How do we do this? Well, let's take the key of C Major as an example, and try to find its related keys in the Circle of Fifths:
The most closely related key to C Major is of course its relative Minor key, A Minor, since they share all their notes! In the Circle of Fifths, you can find the relative Minor key right next to its Major key.
Other than its relative key with which it has all notes in common, every key has 4 "closely related" keys that it shares 6 notes with. Let's look at C Major again, and try to find its 4 closely related keys... Fortunately, this is actually pretty easy to do: just take the keys that are on its right (G Major and its relative key E Minor) and on its left (F Major and its relative key D Minor). And that's it, we have our closely related keys!
So, using the Circle of Fifths, we found out what the key of C Major's 5 closely related keys are: A Minor, G Major, E Minor, F Major and D Minor. We found each of those keys right next to the key of C Major in the Circle of Fifths. It's just as easy to find any key's closely related keys: just find the 5 keys adjacent to it in the Circle of Fifths, and you're done! Modulation between relative and closely related keys, which is called "simple modulation"
can easily be done and, if done right, will almost always sound good. The concrete methods of achieving simple modulation will be discussed in the next section of this article.
We know about modulation between relative and closely related keys now, but what about distantly related keys? Well, those are keys that have less that 6 notes in common with the original key, so that they're not directly related (i.e. they're not adjacent to each other in the Circle of Fifths). They can be indirectly related to our original key, though! Let's take C Major as our original key again, and look at its relationship with the key of D Major, for example... you can see that they're not adjacent to each other in the Circle of Fifths, so they're not closely related keys. However, both C Major and D Major are closely related to G Major, so it's possible to make an indirect transition from C Major to D Major, using G Major as an intermediate! Similarly, transitions can be made between even more distantly related keys, with progressively more intermediate steps of simple modulation. It's also possible to achieve modulation from one key directly to a distantly related key, however; how this is done will be discussed later.
Concerning modal music, the possibilities are practically endless, since a single mode can be be related to many, many other modes. Again, let's use C Major as our example. Each of the seven modes of C Major share the exact same notes, so they can all be easily interchanged! You can move easily from D Dorian to G Mixolydian, for example (remember that the chord progression needs to change as well, in order to express each mode clearly). Then, consider that all seven modes of the F Major and G Major scales share 6 out of 7 notes with all of the modes of the C Major scale... and you can already see the gigantic and extremely complicated web of interchangable closely related modes forming, and we haven't even considered more distantly related modes yet! In practice, however, it's not always easy to switch between modes, since it's not easy to move to a different tonal centre after putting in so much effort establishing your current tonal centre! The general rule here is, therefore: if it sounds good, do it, but if it doesn't, try something else!
B. Parallel Keys
Modulation between related keys is not the only possibility; we can also modulate between "parallel keys"
, which are keys that share their tonal centre. Each key only has one parallel key: the Major or Minor key with the same tonal centre. For example, C Major's parallel key is C Minor; A Minor's parallel key is A Major. Even though parallel keys have only 4 notes in common, modulation between them will still go smoothly because they share the most important note of all: the tonal centre!
Modal music works exactly the same, except that each mode has 6 parallel modes: for example, C Ionian is parallel to C Dorian, C Phrygian, C Lydian, C Mixolydian, C Aeolian and C Locrian. You can interchange at will, providing that your chord progression always accompanies and accentuates the mode you're playing in at the moment... The concept of interchanging modes that share the same tonal centre is also called the "pitch-axis theory"
: you're using a single pitch as an "axis" (tonal centre) that you apply interchanging modes to!
So, now that we understand the concept of related keys and modes, we can start looking into the practical methods of applying modulation to a progression... As stated in the beginning of this article, there are multiple ways to achieve modulation between related keys. We'll be looking at each of these methods in a similar way: we'll learn what the modulation method is and how it works exactly, and after that we'll look at a short tabbed example of the modulation method in practice!
Common Chord Modulation
The first type of modulation we're going to look into, and also the most common one, is called "common chord modulation". First, we'll have a look at what this definition actually means, then we'll look at an example to see how this type of modulation works.
A. What is it?
The name "common chord modulation" speaks for itself really... You guessed it: in common chord modulation, the progression moves from the original key to the destination key through a chord that is shared by both keys! The common chord is called the "pivot chord" (a "pivot" is a term for an object on which something turns or rotates: in this case, a chord on which the key rotates); common chord modulation is therefore also called "diatonic pivot modulation" sometimes.
Now, which chords can be used as pivot chords, if you want to modulate your progression to a related key? Well, the easiest of all is modulating between relative keys, since they share all their notes, they also share all their chords; so if you want to modulate between relative keys, any chord will work as a pivot! When modulating between closely or even distantly related keys, you need to compare the chords from both keys, to see which one are present in both keys. Those are the chords that can function as a pivot! We're going to look at an example of simple modulation (between closely related keys) using a pivot chord below.
Before we look at the modulation example, however, a quick note on modal progressions: they can of course be modulated through common chord modulation as well, but keep in mind that you need to change the extensions to express the destination mode instead of the original mode in your progression! This makes it not always easy to achieve a smooth pivot modulation in modal progressions; different types of modulation are therefore usually better to modulate modal progressions.
Right, an example of simple pivot modulation of a basic tonal progression! Suppose we have a progression in the key of C Major, and we want to modulate it to G Major, a closely related key. The first thing we need to do is compare the chords in both keys. Here they are:
C Major: C - Dm - Em - F - G - Am - Bdim
G Major: G - Am - Bm - C - D - Em - F#dim
From the above scheme, it's easy to deduce that the common chords in these two keys are C, Em, G and Am. So basically, we can use any of these chords in the key of C Major as the pivot chord to modulate to G Major! Let's take a look at a progression in which we perform a common chord modulation like this:
C / G / F / / / Am / Bm / D / / / Em / D / G
C Major: I V IV vi
G Major: ii iii V vi V I
In the above progression, I indicated the chord numbering in both keys. I also underlined the pivot chord where the transition from C Major to G Major is made: the A Minor chord functions as the sixth (vi) chord in C Major, as well as the second (ii) chord in G Major! Up to the Am chord, all played chords belong to the key of C Major exclusively, and after the Am chord the played chords are exclusive to the G Major key.
Before we move on to the next method of modulation, I must stress that you should keep in mind that not every chord that can function as a pivot chord in theory, will offer a smooth transition between keys when used as a pivot in practice! Experimentation is the key here: try out modulating different progressions using different pivots! Do what sounds good to your ear, and ditch what doesn't! This is what music is about, after all...
Common tone modulation
If you understood common chord modulation well, you'll find that you'll have no trouble understanding this type of modulation as well, since it's based on a very similar concept!
A. What is it?
Again, the name "common tone modulation" speaks for itself: whereas common chord modulation was based around a chord that the original and destination keys shared, common tone modulation is based around a single shared note. Even though this sounds a lot simpler than common chord modulation in theory, it is used a lot less in practice, because this modulation technique allows for much more "abrupt" key changes to much less closely related keys.
How does common tone modulation work exactly? Well, usually modulation occurs when in the melody, one note that belongs to a chord in the original key is singled out and sustained, while the other notes in that chord change to form a different chord that belongs to a different key. Both chords share the sustained note, the "common tone" that bridges the original and new keys! Modulation to a parallel key or mode works this way; the tonal centre functions as the shared note stringing the original and new keys or modes together.
Note that the only requirement in common tone modulation is that you modulate between two chords that only share a single note, which is singled out in the melody, and which forms the only tie between the two chords and therefore the two keys... this means, the possibilities for modulations are endless, and by no means restricted to closely related keys! Very "abrupt" modulations to relatively distantly related keys can be achieved through common tone modulation; this is the main reason why common chord modulation, which usually creates "smoother" transitions from one key to another, is more commonly used in tonal music.
We can almost move on to our example, but first we need to assess how this method of modulation would work in modal music. In modal music, you should consider the fact that the modulation possibilities are even vaster, since interchange between tons and tons of modes becomes possible, simply by using a single shared note... The common tone method of modulation is actually very common in modal music, since like I said, switching to parallel modes (also known as "pitch axis" play) falls into this category.
Ok, let's look at an example of a common tone modulation in practice! In the simple tonal example below, I'll be demonstrating modulation using the common tone technique. The tab shows the melody, while the chords in the progression are indicated above it.
C G F
D A G D
The first 2 bars of this short piece are in C Major, and the melody is based on the same I-V-VI (C-G-F) progression I used in my previous example. As you can see in the second bar, the C Major melody ends on a sustained A, which belongs to the F Major chord... Then, in the next two bars, the sustained A is repeated, except it's now part of a D Major chord! This way, we shifted the key of this progression from C Major to D Major, which as we know is not a key that's closely related to C Major... which makes the modulation sound very abrupt. Try playing this example riff yourself, you'll hear exactly what I mean!
Again, I must remind you that not every modulation works for the human ear, even though it might be perfectly valid in theory. This is even more true in common tone modulation than in common chord modulation, since the modulations are far less smooth... Remember: if it sounds good, do it; if not, don't!
We arrive at the last of the 3 methods of modulation that this article assesses, called "direct modulation" or "phrase modulation". Again, we'll start off with a short explanation of what it actually is, followed by a short example.
A. What is it?
Basically, the principle of direct modulation is the simplest of all: a progression is abruptly modulated from its original key to a new, closely related key, without interposition of "linking material" like shared chords and/or notes. It's important to remember that the progression needs to be resolved to its original key's tonal centre, before it can be modulated to the new key... in essence, you need to "finish" the progression before you continue it in another key!
Sounds easy enough, right? Well, it is, and therefore direct modulation is a widely applied method of modulation. First of all, since it requires the progression to resolve before it can be modulated, direct modulation occurs often between clearly defined sections of a music piece (e.g. between phrases, hence "phrase modulation"; or, modulation from a Minor key in the verse of a song, to its relative Major key in the chorus). A second common use of direct modulation is called the "Truck Driver's Gear Change", which is often used in pop music. Basically, it consists of a modulation to the key one or 2 semitones higher than the original key; the song's chorus or theme is then repeated in this raised key, in order to create a climactic (and very cheesy) effect. These two uses can apply to modal music just as well!
As an example of direct modulation, I'll show you a simple "Truck Driver's Gear Change" in action! Let's look at the progression in C Major we've been using for the previous 2 examples:
C Major D Major
C / G / F / / / Am / G / C / / / D / A / G / / / Bm / A / D
Let's pretend that the 4 first bars in C Major are our new pop song's chorus. Now, we want to end the song on a cheerful, cheesy note; how do we do this? Many pop song writers use the simple trick of "Truck Driver's Gear Change" modulation: simply modulate the progression a semitone or two up! This is exactly what we did after our 4 bars of C Major: as you can see, the 4 remaining bars of our progression are in D Major, as every chord simply shifted two semitone steps upwards!
Again, I must remind you that a direct modulation that seems valid on paper won't always automatically sound good as well... But unlike common chord and common tone modulation, direct modulation offers you a lot of liberty! Modulation to closely related keys, parallel keys, even distantly related keys... it can all be done with direct modulation! Still, keep in mind that if you want to write a progression containing a direct modulation, you need to make sure it sounds good above all else.
And there we go! We covered the most important methods of modulating chord progressions... There are other methods than the ones we discussed, but these are the most basic and most commonly used modulation methods, and they should already provide you with sufficient ways of creating your own progressions with varying tonal centres!
With this final installment of music theory, we covered all the theory the Ultimate Guide to Guitar has to offer to you! It's been a very long journey, and it's no shame should you be unable to remember small fractions or even large chunks of all the theory we discussed together; the articles will always be there for you to reread!
Next week, there will be one more installment of advanced guitar technique that we have not yet assessed. After that, the UGG will finish with a short, but vital epilogue... but let's not think of that sad, sad moment yet! Until then, enjoy this last chunk of theory, and rock on!
PS: For almost the last time:
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