Chord Theory

Compiled by Paul Zimmerman

The Fretboard : Keys - The Circle Of Fifths : Chord Construction
Chord Substitions : Modes : Chord Voicings

The Fretboard

The first thing that you will need to learn is the notes on the fretboard. It is very important to any theory on guitar to know where the notes are on the neck. At first, memorize the notes on the first couple of strings. Then figure out what the notes on the rest of the strings will be. In a pretty short amount of time you should be able to do that. In time you'll develop more of a feel for where the notes fall, without having to think about it, but that's not necessary for chord theory. What you really need to be able to do is to be able to figure out what notes you're playing in a given chord.

e||-F--|-F#-|-G--|-G#-|-A-|    Note positions
B||-C--|-C#-|-D--|-D#-|-E-|     on fretboard
G||-G#-|-A--|-A#-|-B--|-C-| (# = sharp, b = flat)
D||-D#-|-E--|-F--|-F#-|-G-|
A||-A#-|-B--|-C--|-C#-|-D-|-D#-|-E-|-F-|-F#-|-G-|
E||-F--|-F#-|-G--|-G#-|-A-|-A#-|-B-|-C-|-C#-|-D-|

Notice that there is a full step between all notes except for B and C, and E and F. For the sake of simplicity I have only shown sharps, but it is important to understand where the flats are. A# is equal to Bb. D# is equal to Eb. B# is equal to C, and Cb is equal to B. Once again, for the purpose of chord theory, it is not necessary to be instantly familiar with every note on the fretboard. What is necessary is to be able to figure out the notes of any given chord that you are playing.

Keys - The Circle Of Fifths

The next step in understanding any guitar theory is to understand the circle of fifths. Its importance is that it shows several important concepts. First, it is used in determining scales. Second, it is used to determine which chords are in any given key. Third, it is the basis for chord substitutions. To begin with, I'll demonstrate how the circle of fifths is used in a blues progression in G (something that hopefully everyone is familiar with). Twelve bar blues in G begins with 4 bars of G, 2 bars of C, 2 bars of G, one bar of D7, one bar of C, one bar of G, and finally one bar of D7 (as shown below). This progression is also commonly known as a I - IV - V progression.

G - G - G - G - C - C - G - G - D7 - C - G - D7

If you are not familiar with this progression, learn it. It is one of the most basic building blocks in rock music. Traces of it can be found in everything from Led Zeppelin to doo-wop to surf music to Eric Clapton. The next diagram shows the chords that are in the key of G.

G(I) A(II) B(III) C(IV) D(V) E(VI) F#(VII)

As you can see, the G is the I, the C is the IV, and the D7 is the V in the I - IV - V progression. Any F chords played in the key of G need to be sharpened, otherwise they are considered to be out of key.

In the same way, the circle of fifths shows which notes need to sharpened or flattened in chord constuction. To form a major chord, the first, third, and fifth notes of the scale need to be played. In the case of Gmajor (or just G as it is commonly called), a G note would be 1, a B note would be 3, and a D note would be 5.

e|--|--|oo|--| G~I  As you can see, the open G
B|--|--|--|--| B~3  chord is made up entirely of G,
G|--|--|--|--| G~I  B, and D notes (I, 3, and V).
D|--|--|--|--| D~V  Note that any G chord requires
A|--|oo|--|--| B~3  a VII note to be played would
E|--|--|oo|--| G~I  be an F#, not an F.

For the third part, the Circle of fifths gives an indication of when to play minors, etc. The following list shows some guidelines.

I = major II = minor7 III = minor7 IV = major V = dominant7 VI = minor (known also as the relative minor)
VII = diminished

Later on I will show some substitution rules for incorporating more unusual chords into a progression. It is important to remember that these rules are only general guidelines. If you look at the chords of some songs that you know, you will probably see that as a general trend, these rules are followed, but on many occasions they aren't. One thing to keep in mind: a chord progression may be in the key of A (A is the I chord) without playing an A chord first. Look at the following example.

E - E - A - D

This the chord progression in Lola, by the Kinks. In this case, it is in the key of A (A = I, D = IV, E = V). This shows that the first chord played in a progression does not determine the key. Another example is the IIm - V - I chord progression, which is one of the most common in western music. As you can see, it starts on the IIm chord. I will represent the circle of fifths in chart form, as would be read clockwise from 12 o'clock.

C - no sharps or flats G - F# D - F#, C# A - F#, C#, G# E - F#, C#, G#, D# B - F#, C#, G#, D#, A# F# - F#, C#, G#, D#, A#, F Db - Bb, Eb, Ab, Db, Gb Ab - Bb, Eb, Ab, Db Eb - Bb, Eb, Ab Bb - Bb, Eb
F - Bb

Notice the spacing between chords is the same for each key. Here is the example again in the key of G.

G(I) A(II) B(III) C(IV) D(V) E(VI) F#(VII)

Notice that there is a whole step between all chords except between III and IV, and between VII and I. This will be true for all keys. That pattern is also the same as that for the major scale. The above diagram shows the notes contained in the G major scale.

The VI chord is called the relative minor, because it shares many notes with the tonic (I chord). If C were the tonic, Am would be the relative minor. If you play one after the other, you will notice they sound good together. If something is played in an Am key, you use the exact same chords as if it were being played in the key of C. In this way, you can determine all of the minor keys as well from the circle of fifths.

Chord Construction

A chord is a group of three or more different notes played together. Every chord is based on a specific formula which relates back to the major scale after which it is named. As shown earlier, the formula for a major chord is 1 3 5 hence a G major (GM) chord consists of the first, third, and fifth notes of the G major scale, G B D (refer to the circle of fifths chart).Note that the ROOT note is the note after which the chord is named (the 1 note). The formula for a minor chord is 1 b3 5. In the case of a G minor (Gm) the notes would be G Bb D. Also, a G flat major (Gb) is Gb Bb Db, therefore a Gbm (G flat minor) would be Gb Bbb Db, or Gb A Db. There are many cases where a flattened note has to be flattened again according to the chord formula. Diagrams of the most common chords are available.

The following is a chart of chords which have a slight alteration to one of the given formulas, and are therefore called altered chords.

Chord NameChord Formula	Example
Major flat five1 3 b5	Cb5: C E Gb
Minor seven flat five1 b3 b5 b7	Cm7b5: C Eb Gb Bb
Seven sharp five1 3 #5 b7	C7#5: C E G# Bb
Seven flat five1 3 b5 b7	C7b5: C E Gb Bb
Seven sharp nine1 3 5 b7 #9	C7#9: C E G Bb D#
Seven flat nine1 3 5 b7 b9	C7b9: C E G Bb Db
Seven sharp five flat nine1 3 #5 b7 b9	C7#5b9: C E G# Bb Db
Nine sharp five1 3 #5 b7 9	C9#5: C E G# Bb D
Nine flat five1 3 b5 b7 9	C9b5: C E Gb Bb D
Nine sharp eleven1 3 5 b7 9 11#	C9#11: C E G Bb D F#
Minor nine major seven1 b3 5 7 9	Cm9(M7): C Eb G B D
Thirteen flat nine1 3 5 b7 b9 13	C13b9: C E G Bb Db A
Thirteen flat five flat nine1 3 b5 b7 b9 13	C13b5b9: C E Gb Bb Db A

In altered chords, the notes to be altered are always written as part of the chord name, enabling you to construct the chord. For example, Cm7#5b9 (not listed above) is a Cm7 chord with the fifth sharpened and the ninth flattened. Another type of alteration occurs when chord symbols are written thus: G/F#, or C/G. Finger the chord to the left of the slash, then change the note on the bass string to the note to the right of the slash. Here are the substitution rules for altered chords:

9, b9, or #9 replaces 1 sus2, sus4, or b3 replaces 3
b5, #5, #11, or 13 replaces 5

Chord Substitutions

Remember this chart from earlier? It shows the common chords for each key.

I = major II = minor7 III = minor7 IV = major V = dominant7 VI = minor (known also as the relative minor)
VII = diminished

The following chart displays common chord substitutions for the M, m, m7 and diminished chords shown above.

Major: 6, M7, M9, sus2, sus4, sus2sus4, Madd9, 6add9, M7#11, M9#11 Minor: m, m6, mM7, mM9, mM7#11, m6add9 m7: m7, m9, m11, m13, m7#5, m7b5 7: 9, 11, 13, 7sus4, 7sus2, 13sus4, 7b5, 7#5
dim: m7b5

I haven't included everything, because you can easily tell which category a chord belongs to. Cmajor13 substitutes for any major (I, IV). G7b5b9 susbstitutes for a dominant 7 chord, etc. There are also a few chords that are not shown in the diagrams, but you should be able to figure those out too. Cmajor 13 is 1 3 5 7 9 and 13, G7sus2 is 1 2 5 b7, etc. It is important to keep in mind that these are guides, not rules, and there will be many times when you'll want to break them, which is fine. If it sounds good, then it is right. The following is a more in depth description of several chords and their common uses.

Major 7 - gives a fuller sound, often used in jazz Major 9 - used in jazz Major6add9 - used often in country and in jazz. Suspended chords usually resolve to the major, often used to break up a static vamp (instead a playing C the whole time, switch from C to Csus to C, etc) Minor - sad chord m6 - used in funk m7 - used in funk m7#5 - used in fusion m11 - used in funk m(M7) - dark, moody Ninth - used in funk Augmented - connecting chord Diminished - passing chord 7sus2 - used in folk m#5 - often used as a IIIm chord maj13#11 - used in soul 9#11 - chromatic passing chord resolving down a half step, or as a substitute for a IV7 chord 13#11 - same usage as 9#11 M7#11 - dramatic ending chord M7b5#9 - ending chord, or a passing chord to I m7b5 - usually used as a IIm in a minor key 9sus4 (11) - most popular substitution for dominant 7 chords Augmented 7 - V chord in a minor key Diminished - substitute for second half of IV chord measure in the blues, one half step higher (C = I, F = IV, F#dim would be used) The V chord may be substituted on the weak beats (2 and 4) for a Im 7sus4b9 - V chord resolving to Im, or as I chord in Phrygian mode m7#5 - IIIm in the harmonized major scale
13b9 - V7 chord, Alternate from M6 to M7 and back when playing a static I chord

Common chord progressions:

I - IV - V7 and IIm - V - I and IV - IVm - I

This diagram will help to show some fingerings for many of the altered chords. After studying these two examples, you should be able to figure out the rest of the altered chords. The numbers on the frets are the notes, not the fingerings (R = root, 3 = third, etc).

 C9
 +---+---+---+---+---+     +---+---+---+---+---+
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |  b3   |   |   |
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   3   |   |   |     |   |   3   |  b9  b5
 +---+---+---+---+---+     +---+---+---+---+---+
 |   R   |  b7   9   5     |   R   |  b7   9   5
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |   |   |  #9  #5
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |   |   |   |  13
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |   |   |   |   |
 +---+---+---+---+---+     +---+---+---+---+---+


 C
 +---+---+---+---+---+     +---+---+---+---+---+
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |   |   |   |   |
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |   |   |   |   |
 +---+---+---+---+---+     +---+---+---+---+---+
(5)  R   |   |   |  (5)   (5)  R   |  b7   2  (5)
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |   |   7  b3   |
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   5   R   3   |     |   |   5   R   3   6
 +---+---+---+---+---+     +---+---+---+---+---+
 |   |   |   |   |   |     |   |   |   |   4   7
 +---+---+---+---+---+     +---+---+---+---+---+

Modes

The last topic I'm going to cover is modes. The reason I'm including them is that they fit in so well with chord theory (as does the major scale, which I mentioned much earlier). A mode is simply a displaced scale. The ones I will show are a C major scale (no sharps or flats), displaced to D, E, F, etc. The modes are commonly used in jazz improvisation, but they also appear very often in rock music. The one thing to remember about soloing in the modes is that you need to change modes according to the chord changes, and also you need to resolve to the root when you make these changes. The diagrams below show one position for the modes, with the most up-to-date method of fingering (but certainly not the only). If you are soloing in the F - Lydian mode, and need to change to G - Lydian, you just slide everything up two frets.

I = Ionian II = Dorian III = Phrygian IV = Lydian V = Mixolydian VI = Aeolian
VII = Locrian

 A - Aeolian            B - Locrian     
 E  A  D  G  B  e       E  A  D  G  B  e
 ================       ================
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  |  |  |      (*) *  *  *  |  |
 +--+--+--+--+--+      7+--+--+--+--+--+
 |  |  |  |  |  |       *  *  |  |  *  *
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  |  |  |       |  | (*) *  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  |  |  |       *  *  *  *  *  *
 +--+--+--+--+--+       +--+--+--+--+--+
(*) *  *  *  |  |       |  |  |  |  |  |
5+--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  |  *  |       |  |  |  | (*) *
 +--+--+--+--+--+       +--+--+--+--+--+
 *  * (*) *  |  *       |  |  |  |  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 *  *  |  |  *  *       |  |  |  |  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  *  *  |  |       |  |  |  |  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  | (*) *       |  |  |  |  |  |
 +--+--+--+--+--+       +--+--+--+--+--+


 C - Ionian             D - Dorian
 E  A  D  G  B  e       E  A  D  G  B  e
 ================       ================
 +--+--+--+--+--+       +--+--+--+--+--+
(*) *  |  |  |  |      (*) *  *  *  |  |
8+--+--+--+--+--+    10 +--+--+--+--+--+
 |  |  *  *  |  |       |  |  |  |  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 *  * (*) *  *  *       *  * (*) *  *  *
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  |  |  |       *  |  |  |  *  *
 +--+--+--+--+--+       +--+--+--+--+--+
 *  *  *  *  *  *       |  *  *  *  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  | (*) *       |  |  |  | (*) *
 +--+--+--+--+--+       +--+--+--+--+--+


 E - Phrygian           F - Lydian
 E  A  D  G  B  e       E  A  D  G  B  e       
 ================       ================
 +--+--+--+--+--+       +--+--+--+--+--+
(*) *  *  *  |  |      (*) |  |  |  |  |
12--+--+--+--+--+       +--+--+--+--+--+
 *  |  |  |  *  *       |  *  *  *  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 |  * (*) *  |  |       *  * (*) |  *  *
 +--+--+--+--+--+       +--+--+--+--+--+
 *  *  *  |  *  *       |  |  |  *  |  |
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  *  |  |       *  *  *  *  *  *
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  | (*) *       |  |  |  | (*) |
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  |  |  |       |  |  |  |  |  *
 +--+--+--+--+--+       +--+--+--+--+--+
 |  |  |  |  |  |       |  |  |  |  |  |
 +--+--+--+--+--+       +--+--+--+--+--+


 G - Mixolydian  
 E  A  D  G  B  e       
 ================
 +--+--+--+--+--+     The root notes are
 |  |  |  |  |  |     in parentheses ().
 +--+--+--+--+--+
 |  |  |  |  |  |     The number on the
 +--+--+--+--+--+     left shows what
(*) *  *  |  |  |     fret number to
3+--+--+--+--+--+     start at.
 |  |  |  *  |  |
 +--+--+--+--+--+
 *  * (*) *  *  *
 +--+--+--+--+--+
 |  |  |  |  *  |
 +--+--+--+--+--+
 *  *  *  *  |  *
 +--+--+--+--+--+
 |  |  |  | (*) *
 +--+--+--+--+--+

Notice the repeating shapes of the modes. Unlike the scales you may have previously learned, there is a repetitive pattern to the modes that makes them easy to remember. A seven string guitar would actually show the relationship between modes more clearly. This is what the Aeolian mode would look like on a seven string guitar:

?||---|-*-|---|-*-|-*-|---|---|
?||---|-*-|---|-*-|-*-|---|---|
?||---|-*-|-*-|---|-*-|---|---|
?||---|-*-|-*-|---|-*-|---|---|
?||-*-|---|-*-|---|-*-|---|---|
?||-*-|---|-*-|---|-*-|---|---|
?||-*-|---|-*-|---|-*-|---|---|

There are seven different modes listed above, each one has this pattern, only slightly altered: they each start at a different fret, and at a different spot in the above pattern. Since there are only six strings, the seventh pattern is left off. Also, unlike the fictional guitar in the above example, the B and high-e strings are tuned higher, so the pattern on those two strings is pushed up one fret higher. This is following the pattern first shown in the circle of fifths. Each "+" represents a half step:

I++II++III+IV++V++VI++VII+I....etc

If C is the I chord, then the III and IV chords will be E and F, and the VII chord will be B (notice that there is only a half step from E to F, and from B to C). Therefore the above diagram could also look like this, using Roman numerals:

?||----|-II-|----|III-|-IV-|----|----|
?||----|-VI-|----|VII-|-I--|----|----|
?||----|III-|-IV-|----|-V--|----|----|
?||----|VII-|-I--|----|-II-|----|----|
?||-IV-|----|-V--|----|-VI-|----|----|
?||-I--|----|-II-|----|III-|-IV-|----|
?||-V--|----|-VI-|----|VII-|-I--|----|
                             ^^
                             ||
          I put these in to show why there
          are so many different fingerings
          for the same scales. Just as in
          tuning, if you go down one string
          and back five frets, you get the
          exact same note.

A very good way to practice the modes (or any scale) is to do backsteps. Play the first four notes of the scale, then the 2nd - 5th, then the 3rd - 7th, etc, all the way up, then backwards all the way down. In tab for the Ionian mode in G:

e||-----------------------------------------|
B||-----------------------------------------|
G||-----------------------------------------|
D||-------------------------------4-----4-5-|
A||-------3-----3-5---3-5-7-3-5-7---5-7-----|
E||-3-5-7---5-7-----7-----------------------|


e||-----------------------------------------|
B||---------------------------------------5-|
G||---------------4-----4-5---4-5-7-4-5-7---|
D||---4-5-7-4-5-7---5-7-----7---------------|
A||-7---------------------------------------|
E||-----------------------------------------|

e||-----------------------5-----5-7---5-7-8-|
B||-----5-7---5-7-8-5-7-8---7-8-----8-------|
G||-5-7-----7-------------------------------|
D||-----------------------------------------|
A||-----------------------------------------|
E||-----------------------------------------|

and then repeat in reverse order. The best modes to concentrate on at first are the Ionian, Dorian, and Aeolian. These are the most common, and often are used in jazz improvisation.

Chord Voicings

One way that rhythm players keep things interesting is to use different chord voicings (ie. different ways of playing the same chord). This is a very common technique for jazz playing, as it allows the rhythm player to essentially improvise different ways of playing the exact same chords. In the earlier diagrams I show at least two ways of playing every chord, but there are many more ways of playing them. For this, I recommend a chord encyclopedia. The best one I've seen is the one put out by Progressive, called something similar to 'Guitar Chords'. [Alternatively, the very simple Ultimate Guitar Chord chart or a chord dictionary are available]

Well, that about wraps it up. Hope this helps.