The next step in understanding any guitar theory is to understand
the circle of fifths. Its importance is that it diagrams 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
- |G |G |G |G |C |C |G |G |D7 |C |G |D7 |
a I - IV - V progression. 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.
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 sharped, otherwise they are considered to be out of key.
In the same way, the circle of fifths shows which notes need to
sharped or flatted 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||---|---|-o-|---| G (1) As you can see, the open G chord
- B||---|---|---|---| B (3) is made up entirely of G, B, and D notes
- G||---|---|---|---| G (1) (I, 3, and 5). Note that any G chord
- D||---|---|---|---| D (5) requires a 7 note to be played would
- A||---|-o-|---|---| B (3) be an F#, not an F.
- E||---|---|-o-|---| G (1)
For the third part, the Circle of fifths gives an indication of when
to play minors, etc. The following chart shows some guidelines.
Later on
- VI = minor (known also as the relative minor)
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.
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.
Since I don't have very good graphics capabilities here, I will
represent the circle of fifths in chart form, as would be read
clockwise from 12 o'clock.
- F# (Gb) - F#, C#, G#, D#, A#, E# (F)
Notice the spacing between chords is the same for each key. Here is
the example again in the key of G.
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 mionr keys as
well from the circle of fifths.
