4.3 · Chords of the Key

Why the 7th chord is diminished

The major scale's step pattern decides each chord's quality, so it's the same in every key. Build a chord on all seven degrees, and they come out in three qualities: major on 1, 4, and 5, minor on 2, 3, and 6, and diminished on 7.

Three qualities, fixed seats

The seven chords of C major again, labeled by quality this time. Tap around and listen: bright on 1, 4, 5; dark on 2, 3, 6; tense on 7.

The numeral already told you: uppercase major, lowercase minor, ° diminished. This pattern, M m m M M m °, holds in all twelve major keys.

Measure the chords

4 then 3 is major, 3 then 4 is minor. Tap each numeral and read its two gaps.

43CEG74 + 3 = major. That's C.

Why each degree gets its quality

Each gap in a chord covers two steps of the formula: W+W makes 4 semitones, a pair with an H only 3. Where a degree's four letters catch an H decides the quality: the second pair, major; the first pair, minor; both pairs, diminished.

The formula, with steps past 7 starting over: the scale loops every octave. Tap a step to hear it.

That's C: C · E · G.

Every degree would build the same 4 + 4 chord. The three qualities come from the two H's.

Quiz

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The major chords of a major key sit on degrees…

Score 100% on every quiz and game to complete this lesson. A perfect run sticks: a later miss never undoes it.Every chord has a job →