Chapter 2
The perfect fifth is the second most important interval in music after the octave.
When we examine chords, you will see that for major and minor chords, the interval between the root note and the third note of a chord is always a perfect fifth, with seven semitones separation.
Many famous guitarists play just the root note and the note that is a perfect fifth interval above it.
These two-note chords are known as power chords.
The Tonic, the Dominant (perfect Fifth) and the Sub Dominant (perfect fourth) are the foundation on which harmony in western music is constructed.
For diminished chords, which the name implies as having a smaller interval, have 6 semitones separation between the root note and the third note of the chord.
For augmented chords, which the name implies as having an added interval, has 8 semitones separating the root note and the third note of the chord.
The interval between the second harmonic (2X) and the third harmonic (3X) gives the perfect fifth interval.
The frequency ratio of the fifth is 3X/2X=3:2. We saw this interval earlier.
The interval covers five white positions of the C major scale. Seven semitones separate the notes of a perfect fifth.
Key Takeaway
Chords formed at the perfect fifth interval above the Tonic are known in music as Dominant chords and are the most harmonious and essential chords after the Tonic.
For major keys, the Dominant chord is a major chord.
In modern Western music, the Dominant chord is very commonly the penultimate chord in a creation and progresses very naturally to the Tonic chord.
Later, when we examine chords in more detail, we will provide a simple and intuitive method to immediately identify a major fifth interval.