Knowing the theory of the chords of a major key is a huge step in the right direction to understanding music theory and being able to work out and learn songs quickly.
It's also hugely helpful to change the key of a song on the fly too if you think of the chords of any song in numbers.
All major scales have the same pattern.
You start on a note, called the root note. Then you move up in intervals,
Root - Tone - Tone Semitone - Tone - Tone Tone - Semitone
Tone is also known as a step and a semitone is called a half stepÂ
See this blog post for more information on major scales
So the chords of a all major keys have the same pattern too.
Chords or also know as triads of a major key are stacked in 3rds so if we simply think of our major scale in numbers 1 2 3 4 5 6 7 8 (8 being the octave of 1, same note one octave higher)
Our first chord is the 1st, 3rd and 5th notes of the scale. This is the root chord of the scale. It is a Major chord and is given the roman numeral I for 1
1Â 2 3Â 4 5Â 6 7 8
Chord 2, is the 2nd, 4th and 6th note of the scale, the distance between the 2nd and 4th of a major scale is a minor 3rd so chord 2 in a scale is a minor chord. Given the roman numeral ii (lowercase because it is minor)
1 2Â 3 4Â 5 6Â 7 8
We keep doing this throughout the scale
iii = 1 2 3Â 4 5Â 6 7Â 8 (minor chord)
IV = 1 2 3 4Â 5 6Â 7 8 (Major Chord)
V = 1 2 3 4 5Â 6 7Â 8 2 (Major Chord)
vi = 1 2 3 4 5 6Â 7 8Â 2 3 (minor chord)
vii = 1 2 3 4 5 6 7Â 8 2Â 3 4 (diminished chord)
A diminished chord is made up of a Root, Minor 3rd and a flattened 5th also known as a diminished 5th, I will explain this in more detail in a future lesson.
So the chord pattern of all major keys is this
Chords I, IV, V (1, 4, 5) are Major Chords.
Chords ii, iii, vi (2, 3, 6) are minor chords.
Chord vii (7) is diminished.
So lets put this to practical use, below is a list of different major keys and the chords in them.
So if we had this as a chord sequence
|C |G |Am |F |
Changing this into numbers it would be
|I |V |vi |IV |
So we can use this to change the key of the song.
So in the Key of G,
Chord I is G,
Chord V is D,
Chord vi is Em,
Chord IV is C.
So in the key of G the chords would be
|G |D |Em |C |
In the Key of F
|F |C |Dm |Bb |
Using the diagram above it's very easy to work out what chords you need to play to change the key of any song in a major key.
Or if your playing with musicians and someone says.
"This song is in the key of E, The verse is 1, 4 to 5, then in the chorus change the 1 to a 6"
You'll know that need to play, chords E, A to B in the verse, C#m, A to B in the Chorus.
I have another couple of videos showing how to use this system when using a capo to work out what chords you need to play if changing key or coming up with a second guitar part.
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