Excerpt from Ted Greene's
Chord Chemistry
Chord formulas & Families(Page 10)
Every chord has a certain combinatio of tones that distinguishes it from every other chord. These tones may be derived from the major scale with the same root as the chord name. For instance, any minor chord always has the root, b3rd and 5th tones of the major scale with the same letter name. Therefore, an A minor chord has the notes A, C, and E since they are the root, b3rd, and 5th of the A major scale ( remember that the regular 3rd of the A major scale is C# so the b3rd is C). The particular group of tones that is used for the construction of a particuar tye of note is called the FORMULA of the chord; any chord that has 3 tones in the formula is called a TRIAD.
Ear Training(Page 56)
One thing that is very important in learning to recognize the sounds of different kinds of chords and chord progressions. There are some good reasons for this:
1) If you learn to hear different kinds of chords, you will be able to figure out songs "by ear."
2) You will find that the improvement of your musical ear in one area will overlap into other areas. For instance, if you start to recognize the sound of nice chords when you hear them, you will also start being able to hear nice melodies or solo lines too.
3) You will actually learn to anticipate the place where certain chord progressions are going, and which chords will be making the trip.
One first step in ear training is to learn to tell the difference between simple major and minor triads. Practice a few minutes each day playing many inversions of major and minor chords, if you cannot already hear the difference between the two. In a short time, you will be able to hear this difference.
The next step is to practice also the major 7th and minor 7th chords again, comparing differences with the other chords. Notice how closely related the major and major 7th chords are, and also the minor and minor 7th chords. Also notice that the m7 is the same as a major