Diatonic chords (basic modal chords) of the major scale

Chords are basically constructed by stacking 3rds over a chord root. Depending on which of the 3rds are major 3rds or minor 3rds, you will get a major chord, a minor chord or a more special chord type. If you stack 3rds over each tone of a scale using only the scales tones, you will end up with the diatonic chords (basic modal chords) of that scale! These chords are the basic material for a song in that key.

Major Scale: Whole-Steps and Half-Steps

ALL major scales have a half-step between the 3rd and 4th tone and the 7th and 8th (=first) tone. In the C major scale it is naturally this way, because there are half-steps between the tones E and F and between B and C by nature.

Hence, the C major scale does not need any accidentals. All other scales have to be equipped with #'s or b's to move single tones down or up by a half-step to get the scales half-steps back into the right place. In the F major scale for example the B is lowered to Bb, putting the half-step in the sequence F G A Bb back between the 3. and 4. tone.

On the piano keyboard the C major scale only consists of white keys. There is a black piano key between most of the white keys. Between the 3rd and 4th and the 7th and 8th (=first) tone those black keys are missing. On the guitar every single fret is one half-step, so you have to go two frets up or down to move a whole-step.

Click on the red buttons above the staves to change the shown key.

Major 3rds and Minor 3rds

If you want to move up a 3rd, you have to go up two tones in the scale (in the name "3rd" the starting tone is also counted). Because of the position of the half-steps some 3rds will be a whole-step + half-step = minor 3rd (m3), others may consist of two whole-steps = major 3rd (3).

  • Whole-Step + Half-Step = Minor 3rd
  • Half-Step + Whole-Step = Minor 3rd
  • Whole-Step + Whole-Step = Major 3rd

The first 3rd over a root tone already determines, whether it's going to be a minor chord (minor 3rd) or a major chord (major 3rd). Although the chord is not complete yet (for a precise chord symbol a 5th is still missing - see triads), the major third alone already sounds like a major chord, the minor 3rd like a minor chord.

Tonic, Subdominant and Dominant

Please try to memorise, that the major 3rd (and consequently major chords) can only be found on the first, fourth and fifth scale degree of a major scale. Those degrees a commonly known as Tonic (I), Subdominant (IV) and Dominant (V).

I   ...   ...   IV  V   ...   ...

Triads: Major, Minor (m), Diminished (dim)

Major 3rd (3) + minor 3rd (m3) = perfect 5th (5). Two minor 3rd on top of each other result in a diminished 5th (b5). Now we have complete chords with a root (1), 3rd and 5th:

  • Roor, Major 3rd, (perfect) 5th [ 1 3 5 ] = Major Chord
  • Root, Minor 3rd, (perfect) 5th ( [ 1 m3 5 ] = Minor Chord  (m)
  • Root, Minor 3rd, Diminished 5th [ 1 m3 b5 ] = Diminished Chord  (dim)

General sequence for triads

Because the chord types stay the same through all different keys, you can memorise them in a general form. You should really learn this sequence by heart! The diatonic triads of a major scale are:

I   IIm   IIIm   IV   V   VIm   VIIdim

Not a diatonic chord of a major scale: the augmented chord (aug)

Another chord type for triads (besides major, minor and diminished) is the augmented chord. With two major 3rds on top of each other it is a major chord with an augmented 5th (#5). It doesn't occur as a diatonic chord of the major scale, but still you will come across that chord in more complex harmonical contexts. Contrary to the dim it is mostly written with an "aug" in the chord symbol (or #5 or +5 or just + ).

7th Chords: Major 7, Minor 7, V7, Half-Diminished

Perfect 5th (5) + Minor 3rd (m3) = Minor 7th (7)
Perfect 5th (5) + Major 3rd  (3)  = Major 7th (maj7)

To make it simpler, you can count backwards from the root tone (or an octave above): you will find the major 7th (maj7) a half-step below, the minor 7th a whole-step below the root (or its octave).

General sequence for 7th chords

Because the chord types stay the same through all different keys, you can memorise them in a general form. You should really learn this sequence by heart! The diatonic 7th chords of a major scale are always:

Imaj7  IIm7  IIIm7  IVmaj7  V7  VIm7  VIIm7b5

The Dominant 7th Chord (V7)

Only on the 5th scale degree we can find a major chord with a minor 7th. This chord is commonly known as dominant 7th chord or just "five-seven".

The Half-Diminished Chord m7b5

While examinating the triads, we named the chord on the VII. scale degree a diminished chord (dim). Now, having a 7th chord, dim leads us to a wrong direction, because the diminished 7th chord (dim7 or also just dim) does also have a diminished 7th (b7) instead of a minor 7th. This diminished 7th chord often occurs in more complex harmonic contexts or as a passing chord between the scale degrees, but it is NOT a diatonic chord of a major scale. The m7b5 chord on the VII. scale degree is called half-diminished chord or just "minor-7-flat-5".

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