The 7 chords in a key
Concept
Stack thirds on each note of the major scale and you get 7 chords. The pattern is always: Major, minor, minor, Major, Major, minor, diminished — written as I ii iii IV V vi vii°.
The pattern is fixed
In ANY major key, the qualities are always: - I — Major (tonic) - ii — minor - iii — minor - IV — Major (subdominant) - V — Major (dominant) - vi — minor (relative minor) - vii° — diminished
In C: C, Dm, Em, F, G, Am, B°. In G: G, Am, Bm, C, D, Em, F#°. Same pattern, different starting note.
Why Roman numerals?
Capital = major, lowercase = minor, ° = diminished. The number is the scale degree.
Writing in numerals instead of letters means a progression like I–V–vi–IV is the same shape in every key — you just plug in the chords. Pop songwriters do this all the time.
The 'three majors' and 'three minors'
Notice the layout: I, IV and V are all major. ii, iii and vi are all minor. vii° is the odd one out.
- I, IV, V are called the 'primary' chords. Together they can harmonize almost any melody in the key.
- ii, iii, vi add nuance and minor color.
- vii° is rare in pop; it shows up more in classical and jazz.
Key takeaways
- •Major key chord qualities: Maj min min Maj Maj min dim. Always.
- •Capital numerals = major; lowercase = minor.
- •I, IV, V are the workhorses; vi is the relative minor.
Glossary
- Diatonic
- Built only from the notes of the current key.
- Scale degree
- The position of a note in the scale (1 through 7).
- Roman numeral analysis
- Naming chords by scale degree and quality, e.g. I, ii, V7.
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