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Chord function/ Substitution

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Illustrious Member
Joined: 16 years ago
Posts: 8184
Topic starter  

Hey all, it's been a while since I've been here!

I was just thinking about a chord progression : I-vi-IV-V-I (C-Am-F-G7-C)  Instead of playing the A minor as a straight forward chord I could use Cmaj6 (C-E-G-A) since it is an inversion of the A minor chord.  

Do you guys agree?

If this is true then would the chord progression be written as I-I6-IV--V-I  or  I--vi1stinv.--IV--V--I

This brings another question to mind.  The I-I6-... could be called a chord subsitution too?

Thanks for your help

Eminent Member
Joined: 19 years ago
Posts: 39

Try it out,does it sound good? But yes you can use it in that progresion if thats the disired effect?   that is a substitution

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Joined: 21 years ago
Posts: 5342


C6 and Am7 share the same actual notes - as you've pointed out - and the only "real" difference between them is that one is a major chord and the other is minor. When we use substitutions, we tend to use chords that are different by only one note - Am for C, F instead of Am, Dm instead of F and Em instead of G being prime examples. Other examples would be Cmaj7 instead of C or Am7 instead of Am, and so on.

When we look at chords which have the same notes, but are just based on a different root, then it starts to get foggy, and with the layout of a guitar neck the way it is you can use exactly the same fingering for C6 and Am.

C6 counts as a substitution, but you do need to use it a little more carefully than a conventional Am substitute because you need to look at how it's going to sound compared to the next chord. If the progression is C6 -> F then the C and the A are common, but the E and the G both resolve to F and the effect is muddier than Am->F where only the E resolves to F.

Check this out for substitution - it's a 12-bar blues-style exercise I use with students:

C          /          Cmaj7          /
Am        /         Am7             Am
F           /         Fmaj7          F
C          /         Cmaj7          /
F          /          Fmaj7          /
F          /          Dm              Dm7
C         /           Cmaj7         C
Am       /           /                 Am7
G         /           Em              Em7
F          /           Dm             Dm7
C         /           Cmaj7         C
G         /                 /                 /

It's not excessively complicated, but it sort of works OK. No doubt some of the jazz players will be able to bring in things like the "Flat 5 substitute" and explain how it works.

In fact - that would be a logical progression to this thread. Let's see where that twelve-bar ends up.


A :-)

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Trusted Member
Joined: 19 years ago
Posts: 63

Yes, you can certainly play the Cmaj6 instead of Am but be aware of the sound.  As Alan Green called attention to, Cmaj6 has the same notes as Am7 and can easily be taken for Am7 depending on the voicing and context.  Fortunately, you have a C major chord preceding, which creates context, so the CEGA voicing will probably sound like a Cmaj6 chord.  

BTW, the I and I6 are not substitutes because they are both I chords ("I6" normally means a 1st inversion I chord triad, but I assume you mean a maj6 chord).  The added 6th is just a "color tone" that does not change chord function or tonic.

You could write the Roman numerals as
I Imaj6 IV V7 I  

(vi653 would be accurate in a spelling sense but not if the chord actually is a variation of the I chord - kind of a grey area in this case)  

Honorable Member
Joined: 21 years ago
Posts: 646

Note that you are actually simplifying the chord progression by "back-substitution" if you do that.

I-vi-IV-V-I is a variation on the standard progression that all others derive from, I-I-IV-V.

I (1-3-5) and vi (6-1-3) are related and can substitute for each other, so

I - I - IV - V  becomes I - vi - IV - V.  

So in a sense you are going back to the roots by using C6 in place of Am7.  Nothing wrong with that.

Helgi Briem
hbriem AT gmail DOT com

Honorable Member
Joined: 20 years ago
Posts: 608

i wouldnt agree you can "use Cmaj6 instead of A minor, vice versa"

just cos they have the same notes and its in an inversion doesnt mean its a good idea to start playing all different inversions of a chord anywhere, because it is such a different sound.

Illustrious Member
Joined: 16 years ago
Posts: 8184
Topic starter  

How can they sound significantly different if they contain the same notes?  I usually like to make my progressions sound a little "different"?  

Illustrious Member
Joined: 20 years ago
Posts: 4921

Two chords containing the same notes can sound different for two reasons: first, the way the chord is voiced on the guitar, and second, the emphasis given to individual notes within the chord.

Let's take Am for example -- you could play any of these:
x 0 2 2 1 0
5 7 7 5 5 5
x 12 10 9 10 x
x x 10 9 10 8
each one will have a different sound, even though they each contain only the notes A, C, and E.

You can get two different sounds out of the SAME inversion by altering the dynamics of individual notes.  This is easiest to do with fingerpicking or hybrid picking, but it can be done with just a pick by palm muting just some of the strings.

When Alan and Serickso are talking about being careful of the sound, they mean in the context of the progression, and the choice of voicing.  If you play this:
x 3 2 0 1 0
and then this:
x 3 2 2 1 0
You're only adding the A note to the previously played C voicing, and it will sound pretty clearly like C6.  If instead you go from
x 3 2 0 1 0
x 0 2 0 1 0
The effect is a bit more ambiguous... if the bass note is sharply struck, your ear may hear it as a chord change to Am7

Chord extensions are the most common type of substitution, and Am7 can be substituted for Am.  You just need to make it clearly sound like an "A" chord root.  If it sounds like C6, it will work in most situations (after all, the chords are synonyms -- they contain exactly the same notes!), but your progression may sound like it's bouncing all over the place.

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Reputable Member
Joined: 20 years ago
Posts: 221

It's not excessively complicated, but it sort of works OK. No doubt some of the jazz players will be able to bring in things like the "Flat 5 substitute" and explain how it works.

In fact - that would be a logical progression to this thread. Let's see where that twelve-bar ends up.

I'm incredibly lazy, so here's the simple explanation for those of you not in the know. I'll leave it up to someone else to put it into practice.

1. Find a ii-V-I ("I" doesn't nessecarily mean the I of the key). Let's say that you find a B7-E7-A somewhere.
2. Find the b5 of that V in the middle there. If it's an E, the tritone will be Bb.
3. Play the new progression, B7-Bb7-A.

Why does this work? Let's go over a few facts first...

The dom7 chord is made up of 4 notes - the 1 3 5 and b7.
There is a tritone interval between the 3 and b7.
Because the tritone is symmetrical (6 semitones or 3 tones apart in a 12 semitone system), we can invert it without changing the interval.


Now, let's apply this to the first example.

The E7 is made up of an E, G#, B and D.
The G# and D are separated by a distance of a tritone.
Inverted, the D and G# are separated by a distance of a tritone.
Now let's work backwards. Let's treat the D as the 3 and the G# (Ab) as the b7. This gives us the Bb as the new root and the F as the new 5.

The only really important notes in a dom7 chord are the 3 and the b7.

You can apply this to almost any dom7 chord at all. Your mileage may vary though.

Oh, and this is VERY similar to the way diminished chords work. The only difference is that dim chords have two sets of tritones at equal distances, so they can effectively be substituted/inverted using any of the notes as the root.