Substitute, one of my favorite Who songs! I actually got to play drums on that song at a benefit gig back in the 2000s and had a blast channeling my best Keith Moon!! However, we are going to talk about substituting chords today and not an alter ego.

Understanding a little bit of how music works gives you knowledge of which chords you can substitute to enhance the message or mood of the lyrics. In this blog we will discuss parallel minor and major chord substitutions and (dare I say it) other inter-modal substitutions.

Substitutions and Functional Harmony

Functional harmony plays a very important roll in chord substitutions. For instance, say you have a chord progression in the key of C major including the chords C, Am, F, G (I, vi, IV, V). This progression repeats three times over a 12 bar verse and each chord is a full bar. You want to change up a chord on the third line of the verse to emphasize the lyrics and add interest. You want to change the IV (F) chord, which is the subdominant chord (see previous blog). We would first look at other subdominant chord choices in C major; we have the vi and the ii chords. The vi chord is the previous chord in the verse so we try the ii (Dm) chord. We have C, Am, Dm, G (I, ii, vi, V), however, the change between Am and Dm pulls too much toward the key of A minor and is too sad sounding. So you need another subdominant functioning chord.

We will look to the parallel C minor key and the VI (Ab) chord. This makes the chords from the third line C, Am, Ab, G (I, vi, bVI, V). This works as the root notes from the Am, Ab, and G chords move down by half steps (by semi-tones) and gives you the mood you were looking for. We borrowed the bVI chord from the parallel minor key which has the fancy name of modal interchange. A modal interchange between C major and C minor is different from a key change because we still have the C note as the Root note in both modes.

In the example above you hear a 12 bar chord progression in C with C Am F G each chord taking one bar (in 4/4 meter).

Bars 1 to 12 are from 0 to 23 seconds
Bars 13 to 24 are from 23 to 46 seconds and Dm (ii) substitution is at 42 seconds. C Am Dm G in Bars 21 to 24.
Bars 25 to 36 are from 46 seconds to 1 minute and 9 seconds and the Ab substation chord is at 1 minute and 5 seconds. C Am Ab G in bars 33 to 36.
Bars 37 and 38 are the outro C G7 Cmaj7 (I V7 IM7)

So we have not talked about modes at all in this blog series other than noting that the major scale is the Ionian mode and the natural minor scale is the Aeolian mode. I am not going to go into great detail of modal theory, but you can learn more in the YouTube linked below. Understanding modes is one of those topics that is harder to learn than it is to understand and use. The link below discusses the relative modes (one scale rearranged) and parallel modes (based on a common root note). The main take away is both relative modes and parallel modes are the sources for chord substitutions and key changes (which is a different topic).

Let’s look again at the parallel modes of C major (Ionian) and C minor (Aeolian). In Table 1 below you will see the notes of the C major (Ionian) scale noted with the intervals of the major scale and the chords harmonized on the C major scale. Also, we see the notes of the parallel C minor (Aeolian) scale with the scale intervals and the chords harmonized on the C minor scale.

Table 1

Scale Degrees		1	2	3	4	5	6	7
Major	Notes	C	D	E	F	G	A	B
	Intervals	R	2	3	P4	P5	6	7
	Chords	C	Dm	Em	F	G	Am	B^o
Minor	Notes	C	D	E♭	F	G	A♭	B♭
	Intervals	R	2	♭3	P4	P5	♭6	♭7
	Chords	Cm	D^o	E♭m	Fm	Gm (G7)	A♭	B♭

The main thing you need to take away by looking at this table is the Root of both scales is the C note and therefore the root note of the tonic chord in both scales. The other chords function in the same general manner in both C major and C minor meaning the I, III, and VI chords have a tonic function, the IV and II chords have a subdominant function, and the the V and VII chords have a dominant function.

Seven Modes of Western Music

Let’s look deeper into the use of chords from the parallel modes as substitution chords. First, understand that there are seven modes and there are major (major 3rd in scale), minor (minor 3rd in the scale), or diminished (flatted 5th and minor 3rd). Table 2 list each mode and the type.

Table 2

Major	Minor	Diminished
Ionian	Dorian	Locrian
Lydian	Phrygian
Mixolydian	Aeolian

Tables 3, 4, and 5 below show how the various modes relate to each other as parallel modes (with the same root note). Remember that lower case roman numerals are minor chords and upper case roman numerals are major chords. Also, note that the tables are organized by the brightest sounding mode (Lydian) to the darkest sounding mode (Locrian). See the YouTube link in the Sources section at the end of the blog for a presentation of the lightness and darkness of the different modes.

It should be no surprise that most songs are written in either Major (Ionian) or Minor (Aeolian). In the Sources section at the end of this blog are some links to examples of songs written in the other modes including Lydian, Mixolydian, Dorian, Phrygian, and Locrian. The four modes that are more commonly used (in general order of popularity) are Ionian, Aeolian, Mixolydian, and Dorian where Mixolydian and Dorian are found in a lot of rock and jam-band songs. Phrygian is most commonly used to give a song a latin feel (Carlos Santana, Flamenco, etc.) but is also be used in metal. Locrian is used in metal because of the dark feeling.

Table 3

Mode	Lydian	Ionan	Mixolydian	Dorian	Aeolian	Phrygian	Locrian
1	I	I	I	i	i	i	I^o
2	II	ii	ii	ii	ii^o	II♭	II♭
3	iii	iii	iii^o	III♭	III♭	III♭	iii♭
4	iv#^o	IV	IV	IV	iv	iv	iv
5	V	V	v	v	v	v^o	V♭
6	vi	vi	vi	vi^o	VI♭	VI♭	VI♭
7	vii	vii^o	VII♭	VII♭	VII♭	vii♭	vii♭
	Brightest						Darkest

Table 3 shows the chords resulting from the harmonization of the modal scale (that’s a mouthful). The different modes mean different scale intervals. We still harmonize and build chords using thirds (major and minor 3rds) in most of western music. So in Ionian the ii chord is minor, but in Lydian the II chord is major. This difference in scale intervals is what gives each mode its distinctive sound.

Table 4

Mode	Lydian	Ionan	Mixolydian	Dorian	Aeolian	Phrygian	Locrian
1	C	C	C	Cm	Cm	Cm	C^o
2	D	Dm	Dm	Dm	D^o	D♭	D♭
3	Em	Em	E^o	E♭	E♭	E♭	E♭m
4	F#^o	F	F	F	Fm	Fm	Fm
5	G	G	Gm	Gm	Gm	G^o	G♭
6	Am	Am	Am	A^o	A♭	A♭	A♭
7	Bm	Bdim	B♭	B♭	B♭	B♭m	B♭m

Table 4 shows the parallel mode chords in C. That is, in all the modes, the C note is the root of the scale. This is an example based on the chord structure in Table 3.

Table 5

Mode	Lydian	Ionan	Mixolydian	Dorian	Aeolian	Phrygian	Locrian
1	C▵7	C▵7	C7	Cm7	Cm7	Cm7	Cm7♭5
2	D7	Dm7	Dm7	Dm7	Dm7♭5	Db▵7	Db▵7
3	Em7	Em7	Em7♭5	E♭▵7	E♭▵7	E♭7	E♭m7
4	F#m7♭5	F▵7	F▵7	F7	Fm7	Fm7	Fm7
5	G▵7	G7	Gm7	Gm7	Gm7	Gm7♭5	Gb▵7
6	Am7	Am7	Am7	Am7♭5	Ab▵7	A▵7	A♭7
7	Bm7	Bm7♭5	B♭▵7	B♭▵7	B♭7	B♭m7	B♭m7
Notes	▵ = major 7th chord

Table 5 builds on Table 4 where we add the 7th to the chords. This can be very useful one trying to find the best chord to substitue when considering the melody movement and chord choice.

Closing

So, this article presented a ton of material. You will need to look this blog over and over again and will probably need to review some of the previous blogs to get the most out of what has been presented. Please take the time to view the YouTube links as I research for material that I feel best presents the examples and have the best explanation for a general audience.

And like I said at the beginning of the blog, modes and modal interchange is much harder to learn that it is to understand and use.

In the next blog we will look deeper into cadences and begin to discuss turnarounds.

Sources:
https://www.beyondmusictheory.org/

Here is a resource for the various ways chords are identified. One chord may be written in more than one way. https://jazz-library.com/articles/chord-symbols/