The Architecture of Music

The Circle of Fifths

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The Harmonics

The Harmonics and the Sus4 Chord

You may have once heard someone tune a guitar using the harmonics, but probably have never thought about of how important they really are. In all the root chords and inversions diagrammed on the previous section, a harmonic or perfect 5th interval exists between two of the notes. A perfect 5th interval is equivalent to seven semitones and a perfect 4th interval is equivalent to five semitones. All root position chords have a perfect 5th above the root note. And all root 2nd inversions contain the perfect 4th interval above the bass note. All root 1st inversions have a perfect 5th interval in them as well but it moves from chord to chord. Above, the sus4 chord has both a perfect 5th and a perfect 4th interval.