In music, a triad is harmony of 3 different letters. In major scale harmony, the I (one) chord is a major triad. And in the key of C major, the I major chord is C major. The C major triad is spelled in letters: C E G, and in scale degree tone numbers: 1 3 5.
A tetrad is harmony of 4 different letters. In major scale harmony, the I chord is a major seven tetrad. And in the key of C major, the I major seven chord is C major seven. The C major seven tetrad is spelled in letters: C E G B, and in scale degree tone numbers: 1 3 5 7.
For this lesson, Holistic will be defined as Forms that Overlap. The following illustrates the Holistic Overlap of 5 major seven chord forms in 1st Octave scale degree tone numbers on the guitar fretboard.
We’ll end this lesson with a song from Guitar EncycloMedia that applies the I major seven chord to 15 tonal centers.
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Posted by Mike Overly 
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