Diatonic Chords

Each note within the major scale is thought of as being diatonic to that key. When the notes of a major scale are played together, they sound right to the ear. It so follows that if we construct our triads (chords) from the notes of the major scale, these triads will also sound right to the ear.

Major scales consist of seven notes. We use these notes to construct seven triads. As the construction of the triads are restricted to the notes from the major scale, they are referred to as diatonic chords .

Each of the seven chords are named relative to their starting position within the major scale. This starting position is called the Scale Degree .

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

Roman numerals have historically been used for notating scale degrees.

Each triad is constructed by selecting the starting note and then selecting every other note of the major scale.
For example, the chords diatonic to C Major are:

The triad at degree I of C major is C Major

C Major Triad

The triad at degree II of C major is D Minor

D Diatonic Triad

The triad at degree III of C major is E Minor

E Diatonic Triad

The triad at degree IV of C major is F Major

F Diatonic Triad

The triad at degree V of C major is G Major

G Diatonic Triad

The triad at degree VI of C major is A Minor

A Diatonic Triad

The triad at degree VII of C major is B Diminished

B Diatonic Triad

Given that all major scales are constructed using the same pattern of half-steps and whole-steps, the chord type of each scale degree will follow as specific pattern as well. The following diagram shows the chord quality constructed at each scale degree.

Scale Degree Chord Type
I Major
II Minor
III Minor
IV Major
V Major
VI Minor
VII Diminished
VIII Major