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Lesson 7: Major Scale Harmonization Part 1: Triads

Tertian Harmony - Whoa. There's a word you can throw out at cocktail parties. OK, if you don't already know, tertian harmony refers to the harmonic system based on the interval of a 3rd.

An example of this is chords which are constructed by stacking intervals of a 3rd, one on top of another.

Don't worry about being able to spell or define tertian harmony, just be conscious of the concept of stacking 3rds to create harmony for the major scale.


Let's start with triads. These are the most simple chords of western music. These chords are called triads because they consist of three notes; each note spaced a 3rd apart from the one preceding it. Simple definition: triads are three note chords constructed by stacking thirds. There are four basic triads that I'll talk about in this chapter: Major, Minor, Augmented, and Diminished. The table below shows how these triads are constructed.

Triad Quality
Interval Construction
Ascending Stacked Thirds
Examples of Chord Spellings
Major Triad
1 - M3 - P5
M3 - m3
Minor Triad
1 - m3 - P5
m3 - M3
Augmented Triad
1 - M3 - A5
M3 - M3
Diminished Triad
1 - m3 - D5
m3 - m3

Actually there are only seven basic triad spellings: CEG, DFA, EGB, FAC, GBD, ACE, & BDF. You will run into different variations on these, such as CEbG, or DFA, or even GBD. But as far as grouping the notes together, the seven combinations listed above are the only ones. If you don't believe me, try to spell a triad without using one of the above groupings. Triads are built on thirds; you won't have DGbA because G is not a third away from D, it is a diminished fourth. So, instead of saying DGA, you would say DFA, because F is a major third away from D. This information will be another tool in keeping musical concepts clear in your mind.

Try this: Build a minor triad off C. You would know that the notes used in making a C triad are C - E - G. So you take CEG and add the appropriate or needed to make it a minor triad. You know that to make a minor triad you have to start with a minor third interval. C to E is a major third, so you need to lower the E a half-step to make the triad minor - C - E - G.

Say you want to make a diminished triad off D. You know that a diminished triad is constructed by stacking two minor thirds. Start by taking the D triad: DFA. Now check out the construction: D to F is a minor third - that works. Now F to A is a major third. That's not going to work, so lower the A one half-step, making it A. Now your D diminished triad is complete: DFA.

Exercise #1:

On a sheet of blank notebook paper write out the triads in the order that you see them below.


Write this over and over again and spell the triads out loud as you write them. When you've filled the front and back of the paper get a clean sheet and do it again (if you don't have severe writer's cramp). Every chance you get, say these seven triads out loud to yourself. Within two days of doing this you will have these triad spellings Eternally Memorized (whoa).

Next, memorize the quality of the triad: CEG is major, DFA is minor, EGB is minor, etc. These triads are the natural triads in the key of C. Having this information memorized is just one more step to eliminating a lot of on-the-spot thinking.

These exercises in this section should provide you with a good start on understanding the construction of triads, but, for the next couple of weeks or so, make up more of the exercises on paper. Also, when you have spare time, drill yourself verbally.

Exercise #2:

Complete the following triads from the given roots. Use the diagrams on the first page of this chapter if necessary. I've done the first four as an example.

Major triad off A --- AC E

Minor triad off A --- A C E

Augmented triad off A --- A C E

Diminished triad off A --- A C E

Major triad off B

Minor triad off B

Augmented triad off B

Diminished triad off B

Major triad off C

Minor triad off C

Augmented triad off C

Diminished triad off C

Major triad off D

Minor triad off D

Augmented triad off D

Diminished triad off D

Major triad off E

Minor triad off E

Augmented triad off E

Diminished triad off E

Major triad off F

Minor triad off F

Augmented triad off F

Diminished triad off F

Major triad off G

Minor triad off G

Augmented triad off G

Diminished triad off G

Harmonizing the Major Scale Using Triads

Now that you have (or should have) a strong grasp of triads, let's place them in the order in which they occur in the major scale.

Each note of the scale has its own triad, so in every key there are 7 triads (Roman numerals are the standard way to denote these chords): the I chord, the ii chord, the iii chord, the IV chord, the V chord, the vi chord, and the vii

Capital letters indicate major triads, small letters indicate minor triads, and the placed next to a small triad indicates a diminished triad. You'll notice that triads I, IV, and V are major; ii, iii, and vi are minor; and vii is the only diminished triad. The following table should help summarize this in a clearer format. It is extremely important that you memorize this information!

Major Progression
Chord Cymbol
Quality of
major triad
minor triad
minor triad
major triad
major triad
minor triad
diminished triad

Copyright 2001 T.A. Vieira, Jr.
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