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The Three Chord Trick

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What is it?

A lot of guitarists, particularly those from the world of Rock, Folk and Country & Western will tell you that all sorts of straightforward songs can be harmonised with just three chords. A bit of an over-generalisation, but not as much as one might imagine.

How can that over-generalisation be of any use to a Classical Guitarist?

Much of the more playable repertoire in the world of Classical Guitar is based around arpeggios, rather than polyphonic (choral) writing, and an arpeggio is a disembowelled chord.

If you can understand the key of the piece and if you look into each bar of music, you may find that some, or even all, of each bar is based on a chord shape.

This article will show you how to recognise the key, and what chords are likely to be found in the piece as a result.

Recognising the key

My "Key Signature" article will reduce the key signature to a choice of two keys. If the music has occasional accidentals - sharps throughout the piece - it is probably in the minor key, not the major, but in the unlikely event that you get the initial analysis wrong, it will get discovered when you start fitting chords.

What chords?

The three chords in the 3-chord trick are the chords on the tonic, the dominant (5 notes up) and the subdominant (5 notes down). These terms are explained in my "Degrees of the Scale" article.

How does the trick work?

The trick only really works when the music is made up primarily of the diatonic notes of the scale. Music that's chromatic or that changes key won't let the trick work.

Here's an explanation using the key of C, and the chords on the tonic (C), the dominant (G) and the subdominant (F).

These chords contain the following notes...

(*) The F is the seventh degree of the scale, and so the chord is the Dominant Seventh (in this case G7)

Between them, these 3 chords are consonant with any note in the scale of C (every note in the key of C is in one or two of those chords), and any note in the piece that's not a chromatic note will be harmonised by one or two of the above chords.

There is a pleasing symmetry, because the actual notes of the Tonic, Subdominant and Dominant figure in two chords each, and all other notes figure once.

I'll present a more detailed description further down the page.

The inventory of chords for the common Major Keys

Key Signature Key The Three Chords Subdominant Chord Tonic Chord Dominant Seventh Chord
1b F Bb F C Bb - Bb D F F - F A C C - C E G Bb
  C F C G F - F A C C - C E G G - G B D F
1# G C G D C - C E G G - G B D D - D F# A C
2# D G D A G - G B D D - D F# A A - A C# E G
3# A D A E D - D F# A A - A C# E E - E G# B D
4# E A E B A - A C# E E - E G# B B - B D# F# A

The inventory of chords for the common Minor Keys

Key Signature Key The Three Chords Subdominant Chord Tonic Chord Dominant Seventh Chord
1b Dm Gm Dm A Gm - G Bb D Dm - D F A A - A C# E G
  Am Dm Am E Dm - D F A Am - A C E E - E G# B D
1# Em Am Em B Am - A C E Em - E G B B - B D# F# A
2# Bm Em Bm F# Em - E G B Bm - B D F# F# - F# A# C# E
3# F#m Bm F#m C# Bm - B D F# F#m - F# A C# C# - C# E# G# B

There are patterns in these tables...

Working the trick

Suppose that we have a piece in the key of 1# and that we have determined that it is in the key of G major, rather than E minor (*)

Suppose that we have a bar that reads G B D.
Looking at the 1# row in the first table, we can see that this is a perfect match for the chord of G.
There is a good chance that the whole bar, tune, bass and accompaniment, can be accomplished with minimal left hand fingering changes.

Suppose we have a bar that reads E D C.
In the 1# row there is no perfect match, but the C chord hits the spot in two out of three notes. This, then, is likely to be the building block for this bar, and the D is a passing note.
There is a good chance that we'll start and end the bar in a familiar shape. Some finger movement will be needed during the bar, though the basic shape may have a familiar feel.

Suppose we have a bar that reads C E B D.
Here, there is no good match, but the first part of the bar is a good match for the chord of C, and the second part for the chord of G.
There is a good chance that we need a substantial change of hand position halfway through the bar.

(*) Some double checks

Nothing is certain except death and taxes, but there is a very high probability that the last notes in a piece will be based around notes in the chord of the dominant followed by notes in chord of the tonic (the perfect cadence), and there is a high (but not quite as high) probability that the last note will be the tonic.

But what's the point?

What does this tell us as classical guitarists? As you grow your experience, you will realise that bars based on the chords above are built out of a few basic shapes. These shapes are tailored as the bar progresses to include passing notes. A little knowledge of the musical intent of the composer will help you read more accurately and help you get the right fingers in the right places.

See also

The Cadence article

The Degrees of the Scale article

The Key Signature article

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