Major Scale Chord Harmony


How do we identify the key of a song? Chord Harmony. Chord harmony refers to the collection of chords that pertain within a scale. As we will see below the harmonic structure within a scale can be written as roman numerals (scale degrees). This makes it easier to apply to any key.

A key refers to a collection of 7 notes that constitute a major scale. These notes are the building blocks of chords and construct 7 chords in a key.

Major Scale Chord Formula

When we reference harmony we always refer back to the fundamental scale in music - the Major Scale (Ionian Mode).

Major Scale Harmony: I ii iii IV V vi viidim

What does this tell us? The scale degree which the chord is built upon and the tonality of each chord. We can identify the major chords via the capitalised numerals and the minor chords/ diminished chord being the lower case numerals.

  • 1 = Major
  • 2 = minor
  • 3 = minor
  • 4 = Major
  • 5 = Major
  • 6 = minor
  • 7 = diminished

Applying the Formula

Now if we apply the above harmonic formula to the key of C, we can then identify the chords within C major:

C Major Harmony:

C Dm Em F G Am Bdim

I ii iii IV V vi viidim

This harmonic major scale formula can be applied to any of the 12 keys in music. By knowing this information we can identify the key of songs in Major keys. It is also the first step to understanding chordal harmony in modes.

Tips to help you identify a song key:

  • Look out for the two major chords a tone apart ie. the IV & V chords
  • Look out for the two minor chords a tone apart ie. the ii & iii chords
  • Not always but the last chord of a song will 90% of the time tell you what key the song is in