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Modal Theory

Understanding how the modes work is often difficult to do because the modes have multiple functions. Complicating the issue further is that the functions of the modes in traditional (classical music) music theory sometimes differs from the functions of the modes in Jazz music theory. As a guitarist (or any instrumentalist) of today who seeks to fully understand and use the modes for composing / songwriting, improvising, soloing, etc., we need to understand all the functions of modes to use them effectively.

Below is a list of all the possible functions the modes can serve:

In a major key, each standard mode is an extension of the Major scale.
In a Natural Minor key, each standard mode is an extension of the Natural Minor scale.
In a Harmonic Minor key, each Harmonic minor mode is an extension of the Harmonic Minor scale.
In a Melodic Minor key, each Melodic Minor mode is an extension of the Melodic Minor scale.
Any mode can be in its own key.

With all of these various functions the modes can take on, how do you determine which function is in effect at any given time? The answer is: Context. In some contexts a mode may be its own key, in other contexts a mode may simply be an extension of another scale or mode. In the sections below, I¹ll give you example of this, showing you how to determine a mode's current function.

Reference chart 1
Major and Natural minor modes (also known as the standard modes):
Ionian mode = Major scale
Dorian mode = same as the Major scale starting on the 2nd note.
Phrygian mode = same as the Major scale starting on the 3rd note.
Lydian mode = same as the Major scale starting on the 4th note.
Mixolydian mode = same as the Major scale starting on the 5th note.
Aeolian mode = same as the Major scale starting on the 6th note = Natural Minor scale
Locrian mode = same as the Major scale starting on the 7th note.

Using the key of C major as our starting point, the chart below shows all the modal scales derived from the C Ionian scale. Note: The Ionian mode and the Major scale are the same thing and the two terms are often used
interchangeably. Also, the Aeolian mode and the Natural Minor scale are the same thing and the two terms are often used interchangeably. Notice that all the notes in these seven scales are the same. The difference between the modes are distinguished by which note each scale begins.

Reference chart 2
mode: notes of each mode (scale)
C Ionian         C D E F G A B C
D Dorian        D E F G A B C D
E Phrygian     E F G A B C D E
F Lydian         F G A B C D E F
G Mixolydian G A B C D E F G
A Aeolian       A B C D E F G A
B Locrian       B C D E F G A B

Reference chart 3
Harmonic minor modes:
Mode 1 = Harmonic minor scale
Mode 2 = same as the Harmonic minor scale starting on the 2nd note
Mode 3 = same as the Harmonic minor scale starting on the 3rd note
Mode 4 = same as the Harmonic minor scale starting on the 4th note
Mode 5 = same as the Harmonic minor scale starting on the 5th note
Mode 6 = same as the Harmonic minor scale starting on the 6th note
Mode 7 = same as the Harmonic minor scale starting on the 7th note

Reference chart 4
Melodic minor modes:
Mode 1 = Melodic minor scale
Mode 2 = same as the Melodic minor scale starting on the 2nd note
Mode 3 = same as the Melodic minor scale starting on the 3rd note
Mode 4 = same as the Melodic minor scale starting on the 4th note
Mode 5 = same as the Melodic minor scale starting on the 5th note
Mode 6 = same as the Melodic minor scale starting on the 6th note
Mode 7 = same as the Melodic minor scale starting on the 7th note

In the following examples you will see how to determine which mode a piece of music is in. I highly recommend to play and record the chord progressions given and then to improvise a solo / melody over the progression with the given scale / mode. Examples 1, 2, 3 and 4 are all derived from chords in the key of C major, but only 1 example is actually in the key of C major.

Reference chart 5
Here are all of the possible triad chords in the key of C major:
C Dm Em F G Am Bdim
I ii iii IV V vi viiš

Reference chart 6
Mode Diatonic triads
Diatonic triad function
C Major C Dm Em F G Am Bš 
I ii iii IV V vi viiš
D Dorian Dm Em F G Am Bš C 
i ii III IV v viš VII
E Phrygian Em F G Am Bš C Dm 
i II III iv vš VI vii
F Lydian F G Am Bš C Dm Em 
I II iii ivš V vi vii
G Mixolydian G Am Bš C Dm Em F
I ii iiiš IV v vi VII
A Aeolian Am Bš C Dm Em F G 
i iiš III iv v VI VII
B Locrian Bš C Dm Em F G Am 
iš II iii iv V VI vii

Example 1 - Chord progression in C major:
Chord symbols C Am F G C Dm G F C
Chord function in C major: I vi IV V I ii V IV I

Record this chord progression and use C major scales to improvise over it. You will hear the C note (and the C chord) sound like the root of the key (the note that is most at rest.) Your ear wants our little chord progression to end on the C chord.

Example 2 - Chord progression in E Phrygian:
Chord symbols: Em F Em Dm Em F G F Em
Chord function in E Phrygian: i II i vii i II III II i
Chord function in C major: iii IV iii ii iii IV V IV iii

Record this chord progression and use the C major scale to improvise over it. Notice: All of the chords in this example are derived from the key of C major, and can be found in Reference Chart 5. Even though the chords in this example are derived from the key of C major, you will hear that the C note does NOT sound like the root of the key and your ear does NOT want the chord progression to end on a C chord. It wants to end on the Em chord. The C note in the scale sounds more like a passing tone most of the time. It is the E note that sounds like the root of this chord progression. Why is this so? In this example there is no C chord anywhere in the progression. The C chord and the C note are being de-emphasized. Instead it is the E note and the Em chord that is being emphasized, this is what is causing the E note and the Em chord to sound like the root of the key. This is accomplished by repeating the Em chord multiple times.

So the key is not C major, but E Phrygian. We just established that the root is E and not C, but we are not in the key of E major or E minor (because the chords in the progression are not part of either the E major or E minor scales) but all of the chords are a part of the E Phrygian mode.

Another way to look at this is: Since the chords are derived from C major but the root note of the progression is E, then we need to look at where the E note is in a C major scale. The answer is that the E note is the 3rd not of a C major scale. Now we need to determine what mode starts on the 3rd note of a major scale. Look at Reference chart 1 above and you can see that the answer is Phrygian. So we now have our root note of E on the Phrygian mode which makes the key, E Phrygian. Now look at Reference chart 6 and you can easily see how the chords in this example fit nicely in to the E Phrygian key (mode).

Example 3 - Chord progression in F Lydian:
Chord symbols: F G F Em F G F Dm Em F
Chord function in F Lydian: I II I vii I II I vi vii I
Chord function in C major: IV V IV iii IV V IV ii iii IV

Record this chord progression and use the C major scales to improvise over it. Like the E Phrygian example, this example's chords all are derived from the key of C major, and can be found in Reference chart 5. Even though the chords in this example are derived from the key of C major, you will
again hear that the C note does NOT sound like the root note of this example and your ear does NOT want the chord progression to end on a C chord, it wants to end on the F chord. The F note is the root of this chord
progression. In this example there is no C chord anywhere in the progression. The C chord and the C note are being de-emphasized. Instead it is the F note and the F chord that is being emphasized because it is
repeated many times in the chord progression. Therefore, the key is F Lydian, not C major.

We just established that the root is F and not C, but we are not in the key of F major because the chords in the progression are not a part of F major. All the chords are a part of the F Lydian mode. Another way to look at this: Since the chords are derived from C major but the root note of the progression is F then we need to look at where the F note is in the C major scale. The answer is the F note is the 4th note of a C major scale. Now we need to determine what mode starts on the 4th note of a major scale. Look at Reference chart 1 above and you can see the answer is Lydian. So we now have our root note of F of the Lydian mode which makes the key, F Lydian.

Now look at Reference chart 6 and you can easily see how the chords in this example fit nicely in to the F Lydian key mode).

Example 4 - Chord progression in D Dorian:
Chord symbols: Dm G Dm Em Dm G Dm F
Chord function in D Dorian: i IV i ii i IV i III

Chord function in C major: ii V ii iii ii V ii IV

Record this chord progression and use the C major scales to improvise over it.

Like the previous 2 examples, this example's chords all are derived from the key of C major, and can be found in Reference chart 5.
Even though the chords in this example are derived from the key of C major, you will again hear that the C note does NOT sound like the root note of this example and your ear does NOT want the chord progression to end on a C chord, it wants to end on the Dm chord. The C note in the scale sounds more like a passing tone most of the time. It is the D note that sounds like the root of this chord progression. In this example there is no C chord anywhere in the progression. The C chord and the C note are being de-emphasized. Instead it is the D note and the Dm chord that is being emphasized because it is repeated many times in the chord progression. So the key is D Dorian, not C major.

We just established that the root is D and not C, but we are not in the key of D minor or D major because not all the chords in the progression are not a part of D minor or D major scales. All the chords are a part of the D Dorian mode. Another way to look at this: Since the chords are derived from C major but the root note of the progression is D then we need to look at where the D note is in the C major scale. The answer is the D note is the 2nd note of a C major scale. Now we need to determine what mode starts on the 2nd note of a major scale.

Look at Reference chart 1 above and you can see the answer is Dorian. So we now have our root note of D on the Dorian mode which makes the key, D Dorian. Now look at Reference chart 6 and you can easily see how the chords in this example fit nicely in to the D Dorian key (mode).

The best way to remember all of this information is to use it.

Copyright 2002 by Tom Hess. All rights reserved.

Good Luck

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