Chord Construction I: Triads

To this point in the series, we have defined and constructed each type of chord according to a formula based on the major scale with the same root note as the chord.

But each type of chord can also be defined by the intervals it contains.

This post will analyze the intervals contained in the triads covered to this point in the series — major, minor, diminished and augmented.

Common fingerings for the triads, along with instruction on how to play them with any root note were provided in the post entitled Triads and Chord Formulas.

Major Triads

A major triad contains the first, third and fifth degrees of the major scale with the same root note.  So a major chord contains three intervals: 

  • The distance between the first and third notes.
  • The distance between the third and fifth notes.
  • The distance between the first and fifth notes.

For example, a C major chord (fig.2a) contains the notes C, E and G — the first, third and fifth notes in a C major scale (fig.1). 

Fig.1

So a C major chord contains three intervals:

  • The distance between the C and the E (the first and third notes in a C chord and in a C major scale) is a major third (fig.2b). It contains three scale steps (C, D and E) and four half steps between the two notes. 
  • The distance between the E and the G (the third and fifth notes in the chord and the first and flatted third notes in an E major scale) is a minor third (fig.2c). It contains three scale steps (E, F and G) and three half steps between the two notes.
  • The distance between the C and the G (the first and fifth notes in the chord and in a C major scale) is a perfect fifth (fig.2d). It contains five scale steps (C, D, E, F and G) and seven half steps between the two notes.

Fig.2

So a major triad contains a:

  • Major third interval between the first and third notes.
  • Minor third interval between the third and fifth notes.
  • Perfect fifth interval between the first and fifth notes.    

Minor Triads

A minor triad contains the first, flatted third and fifth degrees of the major scale with the same root note.  So a minor chord contains three intervals: 

  • The distance between the first and flatted third notes.
  • The distance between the flatted third and fifth notes.
  • The distance between the first and fifth notes.

For example, a Cm chord (fig.3a) contains the notes C, Eb and G — the first, flatted third and fifth notes in a C major scale.  

So a Cm chord contains three intervals:

  • The distance between the C and the Eb (the first and flatted third notes in a Cm chord and in a C major scale) is a minor third (fig.3b). It contains three scale steps (C, D and E) and three half steps between the two notes. 
  • The distance between the Eb and the G (the flatted third and fifth notes in the chord and the first and third notes in an Eb major scale) is a major third (fig.3c). It contains three scale steps (E, F and G) and four half steps between the two notes.
  • The distance between the C and the G (the first and fifth notes in the chord and in a C major scale) is a perfect fifth (fig.3d). It contains five scale steps (C, D, E, F and G) and seven half steps between the two notes.

Fig.3

So a minor triad contains a:

  • Minor third interval between the first and flatted third notes.
  • Major third interval between the flatted third and fifth notes.  
  • Perfect fifth interval between the first and fifth notes.   

Diminished Triads

A diminished triad contains the first, flatted third and flatted fifth degrees of the major scale with the same root note. So a diminished chord contains three intervals: 

  • The distance between the first and flatted third notes.
  • The distance between the flatted third and flatted fifth notes.
  • The distance between the first and flatted fifth notes.

For example, a C° chord (fig.4a) contains the notes C, Eb and Gb — the first, flatted third and flatted fifth notes in a C major scale.  

So a C° chord contains three intervals:

  • The distance between the C and the Eb (the first and flatted third notes in a C° chord and in a C major scale) is a minor third (fig.4b). It contains three scale steps (C, D and E) and three half steps between the two notes. 
  • The distance between the Eb and the Gb (the flatted third and flatted fifth notes in the chord and the first and flatted third notes in an E major scale) is a minor third (fig.4c). It contains three scale steps (E, F and G) and three half steps between the two notes.
  • The distance between the C and the Gb (the first and flatted fifth notes in the chord and in a C major scale) is a diminished fifth (fig.4d). It contains five scale steps (C, D, E, F and G) and six half steps between the two notes.

Fig.4

So a diminished triad contains a:

  • Minor third interval between the first and flatted third notes.
  • Minor third interval between the flatted third and flatted fifth notes.  
  • Diminished fifth interval between the first and flatted fifth notes.   

Augmented Triads

An augmented triad contains the first, third and sharped fifth degrees of the major scale with the same root note.  So an augmented chord contains three intervals: 

  • The distance between the first and third notes.
  • The distance between the third and sharped fifth notes.
  • The distance between the first and sharped fifth notes.

For example, a C+ chord (fig.5a) contains the notes C, E and G# — the first, third and sharped fifth notes in a C major scale.   

So a C+ chord contains three intervals:

  • The distance between the C and the E (the first and third notes in a C chord and in a C major scale) is a major third (fig.5b). It contains three scale steps (C, E and G) and four half steps between the two notes. 
  • The distance between the E and the G# (the third and sharped fifth notes in the chord and the first and third notes in an E major scale) is a major third (fig.5c). It contains three scale steps (E, F and G) and four half steps between the two notes.
  • The distance between the C and the G# (the first and sharped fifth notes in the chord and in a C major scale) is an augmented fifth (fig.5d). It contains five scale steps (C, D, E, F and G) and eight half steps between the two notes.

Fig.5

So an augmented triad contains a:

  • Major third interval between the first and third notes.  
  • Major third interval between the third and sharped fifth notes.   
  • Augmented fifth interval between the first and sharped fifth notes.   

Triad Interval Construction Summary

A major triad contains a:

  • Major third interval between the first and third notes.
  • Minor third interval between the third and fifth notes.
  • Perfect fifth interval between the first and fifth notes.    

A minor triad contains a:

  • Minor third interval between the first and flatted third notes.
  • Major third interval between the flatted third and fifth notes.  
  • Perfect fifth interval between the first and fifth notes.   

A diminished triad contains a:

  • Minor third interval between the first and flatted third notes.
  • Minor third interval between the flatted third and flatted fifth notes.  
  • Diminished fifth interval between the first and flatted fifth notes.   

An augmented triad contains a:

  • Major third interval between the first and third notes.  
  • Major third interval between the third and sharped fifth notes.   
  • Augmented fifth interval between the first and sharped fifth notes.   

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