SMG Guitar Lesson #9: Why Chords Sound the Way They Do
Similarly, the three minor chords in the key of C are a minor, d minor and e minor. Turning the wheel so that the root note of each chord is at the top of the wheel also reveals that all three chords share the same proportions amongst their intervals. Notice how the structure is slightly different than major chords.
Minor chords can be constructed using the note wheel by turning the note wheel to the desired root note and selecting the intervals Root, b3, and 5th. Again, this is any minor chord regardless of what key we’re talking about.
Minor chord = Root + b3 + 5th
Notice how the only difference between a major chord and a minor chord is that major chords have a 3rd interval, while minor chords have a flat 3rd interval. That’s it!