1. Diatonic Triads and 7th Chords
AP Theory
Diatonic Triads and 7th Chords

2. Diatonic Chords Diatonic – Chords that belong to a specific key/scale
Altered/Chromatic Chords – chords using notes that are not part of a specific key

3. Minor Scale Issues
The problem is the use of the raised 6 and 7 degrees according to where the line leads.
There are many occasions where the melodic minor is used with the raised 6 and 7 leading upward by step and the lowered 6 and 7 leading downward by step
Most of the underlying harmonies in minor conform to the harmonic minor scale (raised 7th degree)

4. Triads in Major
Triads may be constructed using any degree of the major scale as the root
These chords are named by the degree used as the root I, ii, iii, IV, V, vi, vii
The triad type is indicated by the form of the Roman Numeral – uppercase, lowercase
Diatonic Triads types in Major
Major – I, IV, V
Minor – ii, iii, vi
Diminished – vii
Augmented – none

5. Triads in Minor
Because 6 and 7 are variable in minor, construction of these chords are more involved.
Nonetheless there are 7 triads in minor that occur more frequently than the others – all belonging to the harmonic minor scale except the 5th of the III chord
Diatonic Triad typed in minor
Major – III, V, VI
Minor – I, iv
Diminished – ii, vii*
Augmented – none

6. Seventh Chords in Major
Seventh chord types
Major seventh – uppercase roman numeral with a M7
Major-minor seventh – uppercase roman numeral with a 7
Minor seventh – lowercase with a 7
Half-diminished – lowercase roman numeral with a 7
Diminished – lowercase roman numeral with a  7

7. Diatonic Seventh Chords in Major M7 - I M7 and IV M7 Mm7 - V7
m7 - ii7, iii7, vi7
vii 7
 none

8. Seventh Chords in Minor
Because of the variable 6 and 7 degree there are 16 possible diatonic chords in minor
The most commonly used seventh chords on each scale degree belong to the Harmonic minor scale
Common Diatonic seventh chords in Minor
M III M7, VI M7
Mm V7
M i7 and iv7
ii 7
 vii 7

9. Triads in Major and Minor

10. Diatonic Seventh Chords