The scale of a major key consists of 7 notes. For example, in the key of C, those 7 notes are: C, D, E, F, G, A, and B. And we have learnt in Lesson 19, a triad is made up of 3 notes are stacked in thirds.
In other words, we can derive 7 distinct triads from a major key scale, with the root of each triad being the different scale degrees. Here is the example in the key of C:
- Starting with 1 (C): C - E - G
- Starting with 2 (D): D- F - A
- Starting with 3 (E): E - G - B
- Starting with 4 (F): F - A - C
- Starting with 5 (G): G - B - D
- Starting with 6 (A): A - C - E
- Starting with 7 (B): B - D - F
By looking at the intervals between the notes in each of these triad, one can easy figure out the quality of the above chords (review Lesson 19 if necessary):
- C - E - G: C Major, or C
- D- F - A: D minor, or Dm
- E - G - B: E minor, or Em
- F - A - C: F Major, or F
- G - B - D: G Major, or G
- A - C - E: A minor, or Am
- B - D - F: B diminished, or Bdim
To summarize, the pattern for the triads in the key of C is as follows:
1M 2m 3m 4M 5M 6m 7dim
In fact, the same pattern applies for all 12 keys!! That means, in the key of D, the triads that can be derived from the key are: D, Em, F#m, G, A, Bm, C#dim. Try to verify that for yourself!
