Music Theory Part 5 – Chord Formation And The Major Key

Welcome to Part 5 in our educational music theory series.  This post will cover forming chords from the Major scale.  If you’re new to the Major scale, check out part 2.  We’ll be looking at basic chords, made of 3 notes.  These are called triads. The 3 notes are:

  • “Root” – Gives the chord its letter name, ie. a C Major chord’s root note is C.
  • “Third” – Determines if the chord is major or minor.  2 tones away from the root = major third, major chord.  3 semitones (ie. a tone and a half) away from root =  minor third, minor chord.
  • “Fifth” – Solidifies the chord.  Typically 7 semitones, or 3 and a half tones away from the root.  Can be sharpened or flattened to create different types of chord, more on this later.

In practice, finding the 3 notes required to form a chord is very simple.  From your root note, skip the next, the next is your third, skip the next, and the next is your fifth.  So let’s do this now with the C Major Scale.

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

  • So, with C as our root note, we skip the D, to find E as our third (2 tones away from C so thus a Major third)  then skip the F to find our fifth, G.  And there we have a C major chord.  C, E, G
  • Now with D as our root, we skip the E, to find F as our third (3 semitones away from D so thus a minor third) then skip the G to find our fifth, A.  So there we have a D minor chord.  D, F, A

We can continue this process for every note in the scale, and finish up with each scale step now representing a chord as well as a note.  This is essentially what a “key” is.  A key is a group of chords that ‘belong together’


  • The C Major scale contains the notes C, D, E…….etc.
  • The key of C Major contains the chords C Major, D minor, E minor…….etc.

So the resulting chords, the chords in the key of C Major, are –

I               II              III             IV              V             VI              VII
Cmajor     Dminor     Eminor     Fmajor     Gmajor    Aminor    Bdiminished

We’ll cover “diminished” chords in more detail at a later date, for now just be aware that they’re minor chords, with a flattened fifth or “b5” ie. the fifth is a semitone lower than it would be in a normal minor chord.

The main lesson to take from this, is just like the Major Scale was formula-based, the Major Key and its chords are too.
So in ANY Major key, the chord based on scale step 1 is Major,  step 2 minor, step 3 minor, and so on as above.  Thus the formula is as follows : 

IMaj     IImin     IIImin      IVMaj      VMaj     VImin     VIIdim

You should practice applying this formula to other Major scales to create Major keys, and make sure you fully understand it.

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