Functional Harmony – The Relationship Between Chords And Modes

Understanding and using modes on the guitar is very important. It takes many hours of practice memorizing the positions, analyzing qualities of each scale and digesting all the theory that goes with it. It’s important to realize however, that an understanding of modes is not really complete without a good understanding of how they relate to diatonic chords. Chords and scales are very closely linked and a strong understanding of chords aids the use of scales and visa versa. In this post we are going to explore how modes relate to the diatonic chords of a major scale.

Firstly, I’m assuming for the sake of this lesson, that you have a basic understanding of modes. You don’t have to be a master just yet. In fact, hopefully this lesson will help you on your way. If you don’t have at least a basic understanding of modes, please read the post, guitar modes explained. I’m also assuming that you have a basic undertstanding of chords and how they are constructed. If not, please read the post on chord construction before moving on. Assuming you know a bit about both areas, let’s explore their relationship a bit further.

The Basics Of Chords – Triads

A triad is 3 notes played together, usually stacked in thirds. That means that if we are in the key of C, we can form a C Major chord by playing the root note (C), a third up from there (E) and a third up from there (G). That would give us the following three notes that form a C Major chord:

C – E – G

If we wanted to play a C minor chord, we would need to lower the 3rd note of the scale (E) to produce an E flat. We would then get the following for a C minor chord:

C – Eb – G

There are 4 types of triads:

Major – 1, 3, 5
minor – 1, b3, 5
Augmented – 1, 3, #5
diminished – 1, b3, b5

This is just a brief recap of a bit of chord theory.

Now, what we want to do in this lesson is explore the diatonic chords of a major scale. What that basically means is that we are searching for the ‘set of chords’ that fit in any given key, based on the major scale for that key. Let’s look at the key of G.

In the key of G, we have the following 7 notes (G major scale)

G – A – B – C – D – E – F#

Producing the diatonic triads of G Major is quite easy. All we have to do is go through each note of the scale and ‘stack thirds’ on top of each. The important thing to keep in mind is that we MUST stick to the notes of G major, because we are constructing chords in that particular key. Observe the following chart.

1: G – A – B – C – D – E – F#
2: A – B – C – D – E – F# – G
3: B – C – D – E – F# – G – A
4: C – D – E – F# – G – A – B
5: D – E – F# – G – A – B – C
6: E – F# – G – A – B – C – D
7: F# – G – A – B – C – D – E

From that chart, we get this:

1: G – B – D
2: A – C – E
3: B – D – F#
4: C – E – G
5: D – F# – A
6: E – G – B
7: F# – A – C

If we then label those chords, we get the following:

1: G Major
2: A minor
3: B minor
4: C Major
5: D Major
6: E minor
7: F# diminished

What we now have is a pattern of chords that can be applied to any key. Just like the way that modes can be played in different keys. We did this example in the key of G, but what is really important is the chord types and the degree of the scale they relate to. For example, the first chord is a Major chord, the second chord is a minor chord, the third chord is a minor chord, and so on. These ‘numbers’ are usually represented by roman numerals, which looks like this:

I – Maj
ii – min
iii – min
IV – Maj
V – Maj
vi – min
vii – dim

The upper case roman numerals represent a Major chord and the lower case roman numerals represent a minor chord (a diminished chord is technically a type of minor chord because it has a flat 3). Knowing which type of chord goes with which number is really what this whole lesson is about. If you understand the numbers and chords, you can quickly produce the relevant chord in any key for a certain number, for example, the IV chord in the key of C is F major, the vi chord in the key of A is F# minor, the ii chord in the key of E is F# minor, and so on and so on. As well as the roman numerals, there is also a name for each of these degrees of the scale:

I – tonic
ii – supertonic
iii – mediant
IV – subdominant
V – dominant
vi – submediant
vii – leading tone

The reason why each of these degrees have names is because each chord has a certain harmonic function. This means that when used in the right context, they produce a certain mood, or intention.

Ok, let’s just stop there for a minute. That is quite a bit of theory already and we haven’t even really looked at modes yet. So let’s sort out a few priorities for this lesson. Don’t worry about the names (tonic, dominant etc). All you really need to know at the moment is that you can build a chord on each degree of the major scale to produce a set of chords that fit in that particular key. And there is a pattern to this that can be applied to any key. A good thing to do here is to pick a key, figure out the diatonic triads in that key and improvise a few chord progressions. You’ll be surprised at how easy it is. For example, in the key of F, the ‘set of chords’ would be this:

I – F
ii – Gm
iii – Am
IV – Bb
V – C
vi – Dm
vii – E°

Just playing through the chords will give you a sense of how they all work together, which is very important. Hearing them ‘fit together’ is just as important (if not more) as understanding them theoretically.

7th Chords

In our analysis of diatonic chords so far, we have looked at triads. We can apply this whole concept to 7th chords as well. Triads are 3-note chords stacked in 3rds. 7th chords are simply 4-note chords stacked in 3rds. They are called 7th chords because the 4th note is the 7th note of the scale (1-3-5-7). We don’t need to go through all the theory again, but let’s look at the original charts and apply them to the diatonic 7th chords of a major scale. Again, we will use the key of G as our example:

1: G – A – B – C – D – E – F#
2: A – B – C – D – E – F# – G
3: B – C – D – E – F# – G – A
4: C – D – E – F# – G – A – B
5: D – E – F# – G – A – B – C
6: E – F# – G – A – B – C – D
7: F# – G – A – B – C – D – E

From that chart, we get this:

1: G – B – D – F#
2: A – C – E – G
3: B – D – F# – A
4: C – E – G – B
5: D – F# – A – C
6: E – G – B – D
7: F# – A – C – E

If we then label those chords, we get the following:

1: G Major 7
2: A minor 7
3: B minor 7
4: C Major 7
5: D Dominant 7
6: E minor 7
7: F# minor 7 (b5)

Again, let’s derive the pattern from the above information and apply it to the roman numerals:

I – Maj7
ii – min7
iii – min7
IV – Maj7
V – 7
vi – min7
vii – min7 (b5)

If you are a bit confused by the names of the chords. Read the post on chord names to get a better understanding.

Triads vs 7th Chords:

One thing to keep in mind, is that from a functional point of view, triads and 7th chords act the same. That means that the IV chord of any key will have the same ‘effect’, regardless of whether or not you play it as a triad or a 7th chord. Which one should you use then? It really comes down to taste and style. Jazz for example uses a lot of 7th chords (and extensions past that as well, such as 9th chords, but that’s for another lesson) whereas folk music uses mainly triads. Yet both styles are heavily grounded in ‘functional harmony’. Again, it’s important to put this theory to practice. Experiment with playing the 7th chords in a chosen key, then do the same but use only triads. Really listen to how they sound and the emotional qualities of each chord.

Finally – The Role Of Modes:

One thing you should realize (and maybe you already have) is that if you understand the concept of modes and you understand the principles of diatonic chord construction that have been outlined in this lesson, the relationship between the two should be very obvious. In fact, an exporation of chords is almost an exploration of diatonic chords, and visa versa.

Let’s look at the 7 modes of a key and the 7 diatonic chords of a key:

7 Modes

I – Ionian (1 – 2 – 3 – 4 – 5  – 6 – 7)
ii – Dorian (1 – 2 – b3 – 4 – 5 – 6 – b7)
iii – Phrygian (1 – b2 – b3 – 4 – 5 – b6 – b7)
IV – Lydian (1 – 2 – 3 – #4 – 5 – 6 – 7)
V – Mixolydian (1 – 2 – 3 – 4 – 5 – 6 – b7)
vi – Aeolian (1 – 2 – 3b – 4 – 5 – 6b – 7b)
vii – Locrian (1 – b2 – b3 – 4 – b5 – b6 – b7)

7 Diatonic Chords

I – Major 7 (1 – 3 – 5 – 7)
ii – minor 7 (1 – b3 – 5 – b7)
iii – minor 7 (1 – b3 – 5 – b7)
IV – Major 7 (1 – 3 – 5 – 7)
V – Dominant 7 (1 – 3 – 5 – b7)
vi – minor 7 (1 – b3 – 5 – b7)
vii – Minor 7 flat 5 (1 – b3 – b5 – b7)

You should be able to see, that each mode ‘fits’ over the respective chord (with the same roman numeral). Each chord tone from any given chord, is contained in it’s respective mode. For example, the tones of the iii chord (1, b3, 5, b7) are contained in the 3rd mode (phrygian). This really is logical, because we essentially use an identical process to produce chords and to produce modes. Understanding this is really where an understanding of the synergy between modes and chords lies. When a ii chord is being played (min7) you can construct solos using the dorian mode. When a IV chord is being played, the lydian mode is the mode you want. There are of course exceptions to the rule, and once you are really comfortable with chord/scales, bending the rules becomes the challenge, but when starting out, you need to get comfortable with the rules before breaking them.

A Few More Points:

One of the things that most beginners get confused by, is the fact that chords that seem identical, use different modes. For example, the ii chord is a minor 7 chord and the iii chord is also a minor 7 chord. Yet the 2nd mode, Dorian contains only a flat 3 and flat 7, whereas the 3rd mode, Phrygian contains a flat 2, flat 3, flat 6 and flat 7. How can two seemingly identical chords have a different set of notes that fits over each one? It can be a confusing point, but the easiest way to understand it is to understand that with diatonic harmony, each chord has a specific function. Which is why it is also called functional harmony. This basically means that underneath each chord, there are certain things that are implied. An E minor chord functions differently in the key of C, where it is the iii chord, than it does in the key of G, where it is the vi chord. Because these ‘identical’ chords function differently, they require different modes to be played with them. A good thing to keep in mind is that you don’t even need to understand what these ‘functions’ are. They are felt, or heard, more than they are understood.

Don’t think about it too much. This is the beauty of music. We try to understand as much as we can, but at the end of the day, all that matters is what we hear and how that effects us emotionally. The important thing for now is that you understand and put into practice constructing the diatonic chords of any key.