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The circle of fifths

The circle of fifths is an illustration that has been used in music theory pedagogy for hundreds of years. It conveniently summarizes the key signature needed for any key with up to seven flats or sharps.

Minor key signatures

Of course, minor keys can use key signatures, too. In fact, for each major key signature, there is a corresponding minor key that shares its signature. Major and minor keys that share the same key signature are called relative keys. For example, both C major and A minor have zero sharps or flats. A minor is considered the relative minor of C major; likewise, C major is considered the relative major of A minor. Compare the minor key circle of fifths below with the major key circle of fifths above, and you’ll see the remaining relative key pairs.

In order to understand the notations and structures we will be using in describing blues music, it's important to know about key signatures and what are the chord progressions worth with which keys.

Chord Progressions

(In western music typical chord progressions for major scales)

Let's refresh what we've learned so far about scales and chords. A scale is a series of notes that go in an ascending and descending manner. For every scale (major or minor) there are 7 notes, for example in the key of C the notes are C - D - E - F - G - A - B. The 8th note (in this example will be C) goes back to the root note but an octave higher.

Each note of a scale has a corresponding number from 1 to 7. So for the key of C it will be as follows:

C = 1

D = 2

E = 3

F = 4

G = 5

A = 6

B = 7

In order to make a major triad you will play the 1st + 3rd + 5th notes of a major scale. In our example it is C - E - G, that's the C major chord.

Let's have another example this time using the C minor scale:

C = 1

D = 2

Eb (or D#) = 3

F = 4

G = 5

Ab (or G#) = 6

Bb (or A#) = 7

In order to make a minor triad you will play the 1st + 3rd + 5th notes of a minor scale. In our example it is C - Eb - G, that's the C minor chord.

Roman Numerals

Sometimes instead of numbers Roman Numerals are used. We go back to our example and use a Roman Numeral for each note in the key of C:

C = I

D = ii

E = iii

F = IV

G = V

A = vi

B = vii (diminished)

Roman numeral I refers to the chord built on the first note of the C major scale. Roman numeral II refers to the chord built on the second note of the C major scale, and so on. If you notice, some of the Roman numerals are capitalized while others are not. Uppercase Roman numerals pertain to a major chord, while lowercase Roman numerals pertain to a minor chord. Uppercase Roman numerals with a (+) symbol refer to an augmented chord. Lowercase Roman numerals with a (o) symbol refer to a diminished chord.

The I, IV and V Chord Pattern

For each key there are 3 chords that are played more than others known as "primary chords." The I - IV - V chords are built from the 1st, 4th and 5th note of a scale.

Let's take the key of C again as an example, looking at the illustration above, you will notice that note I on the key of C is C, note IV is F and note V is G.

Therefor the I - IV - V chord pattern for the key of C is:

C (note I) = C - E- G (1st + 3rd + 5th note of the C scale)

F (note IV) = F - A - C (1st + 3rd + 5th note of the F scale)

G (note V) = G - B - D (1st + 3rd + 5th note of the G scale)

Also played are:

Dm (note ii) = D - F - A (1st + minor 3rd + 5th note for D scale)

Em (note iii) = E - G - B (1st + minor 3rd + 5th note for E scale)

Am (note vi) = A - C - E (1st + minor 3rd + 5th note for A scale)

and rarely Bm(dim.) which is note vii = B - D - F (1st + minor 3rd + diminished 5th on B scale)

There are many songs that have been written using the I - IV - V chord pattern, "Home on the Range" is one example. Practice playing the I - IV - V chord pattern for every major key and listen to how it sounds as this might inspire you to come up with a great melody for your song. Remember, the ii, iii and vi are also commonly added to the mix to complete the song.

Some Things to Notice

While we’re looking at The Big Map for C, there are a few things to notice.

1) First, let's talk about the blue boxes. Some of the chord variations now appear at the bottom of each box. For instance, C lists the 2 chord, the 6 chord, major 7, major 9, and suspended as possible options, any of which can be played at that location

2) Three blue locations have been added.

• The octagon with C/G inside indicates that this chord quite often follows Dm or F, and then heads for G before going home to C.
• The box labeled F/C and G/C shows that the right hand chord can change while the bass note (C) stays right where it is. This technique, holding a bass note while varying the chord above it, yields many surprising and useful sounds.
• Finally, the little box labeled C/E is often found between F and Dm. It works going either way.

3) The chords with a green background don't belong to the key of C; they come from other keys. They are useful when we want to explore sounds a little "farther from home." You can put a green chord almost anywhere, but when you do, you'll probably want to follow the arrows back toward the blue ones. Your audience will feel good when the chords that seem far from home step back to more familiar ground.

(A word about names: some of the green chords are written as slash chords, like Am/F#, meaning that, on a keyboard, an Am chord would be played by the right hand, and an F# would be played as the bass note by the left hand. This chord can also be written F#m7b5. In general, whenever you take a simple minor chord and move the bass from the root down three half steps, you get a m7b5 on the new bass note.)