Scale tone chords, as the name implies, are piano chords which are comprised (formed) from the tones (notes) of a particular scale (C,D,F#,etc.). They are present in both major and minor keys with the three note major triad always following these rules
The first chord will always be major, the second chord will always be minor, the third chord will always be minor, the fourth chord will always be major, the fifth chord will always be major, the sixth chord will always be minor and the seventh chord will always be diminished.
A diminished chord is formed by combining the 1st (first), b3rd (flatted third), and b5th (flatted fifth) tones (notes) of a major scale.
Based upon these rules, the scale tone chords in the key of C Major would be: C Major, D minor, E minor, F Major, G Major, A minor, and B diminished.
As you can see, these chords are all comprised of the white tones (note) just like the C Major scale.
To find the three note minor triad chords use this rule. The first chord will always be minor, the second chord will always be diminished, the third chord will always be major, the fourth chord will always be minor, the fifth chord will always be minor, the sixth chord will always be major, and the seventh chord will always be major.
So, based upon this the scale tone chords for A minor, which happens to be the related or relative minor key to C Major, would be: A minor, B diminished, C Major, D minor, E minor, F Major, and G Major. As with C Major, all the chords in A minor are comprised of white notes.
I have used the terms “key” and “scale” throughout this lesson. It is important for you to know that these chords are chords which belong to a particular “key”, C Major, A minor, F Major, etc.
They are formed by combining the different intervals (tones or notes) of a major scale. We have already covered the rules for making major and minor chords. And now you’ve learned the interval combinations for diminished chords.
You can click this link scale tone chords and view these chords in all 12 major and all 12 minor keys. For ease of use, I will place the relative minor key in a column to the right of the Major key. Practice all 12 keys, both major and minor.
Learning Scale tone Triads will help with getting an understanding about how everything is connected. This is one of the fundamental music theory subjects you need to learn.