For example, let’s look at a major chord, C major. It consists of the tones C – E – G.
The interval from C up to E is a major third (4 half-steps).
The interval from E up to G is a minor third (3 half-steps).
This interval formula, root + major third + minor third, applies to all major chords. The other chord types have their own formulas:
|Major||root + maj 3rd + min 3rd|
|Major 7||root + maj 3rd + min 3rd + maj 3rd|
|Minor||root + min 3rd + maj 3rd|
|Minor 7||root + min 3rd + maj 3rd + min 3rd|
|Minor major 7||root + min 3rd + maj 3rd + maj 3rd|
|Dominant 7||root + maj 3rd + min 3rd + min 3rd|
|Diminished||root + min 3rd + min 3rd|
|Diminished 7||root + min 3rd + min 3rd + min 3rd|
|Half-diminished||root + min 3rd + min 3rd + maj 3rd|
|Augmented||root + maj 3rd + maj 3rd|
The table above only lists chords that are built using thirds. Of course, you can think of all other types of chords in terms of intervals too.
For example, the interval formula for a suspended chord like Csus4 (C-F-G) is: root + perfect fourth + major second. And a major 6 chord such as Cmaj6 (C-E-G-A) is: root + maj 3rd + min 3rd + major 2nd.
And so on… Figuring out the interval formulas for all the other possible chord types is left as an exercise for the reader.
Alternatively, you can look at intervals this way: A major chord consists of the root, the tone a major third up from the root, and the tone a perfect fifth up from the root. After all, C up to G is a perfect fifth interval.
Personally, I don’t often think about chords in terms of intervals, but I do believe that learning this skill will add to your understanding of the language of music.
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