Watch the Seven Diatonic Chords online guitar lesson by Erich Andreas from Nashville Number System Decoded

Notice that in a major key our 1, 4, and 5 scale notes represent major chords, our 2, 3, and 6 scale notes represent minor chords, and the 7th scale note represents a diminished chord. This is true across all popular genres of music: rock, blues, country, western, jazz, classical, etc. Again, we can go outside of this rule, but for the most part these chords will follow these structures.