Hey Friend,
The perfect fifth interval for the key of C major is G. The triad that coincides is the G major chord, and like the F major chord yesterday, G sounds pretty good supporting a melody written in C.
This is partly because the G note sound wave is still relatively large compared to the waves for the tonic and the perfect octave.
Basically, the larger the sound wave is (the frequency) compared to the tonic (root note), the better it resonates with the tonic or perfect octave. Again, this is all figured out using ratios, and the smaller the ratio, the better the note sounds in relation to its tonic.
Don’t worry, you don’t have to do the math. Just understand that the perfect fifth is still very close in properties to the tonic or octave, so it still sounds really good with either of those notes.
The three notes that make up a G major triad are G, B and D, all notes that are part of the C major scale.
This means the major second (D), perfect fifth (G) and major seventh (B) intervals are the ones that will sound best over a G major chord, but the perfect fourth (F) adds a nice tension.
1 2 3 4 5 6 7 (8)
C D E F G A B (C)
The fifth system with the the major sixth interval (A) doesn’t sound all that great to me, so I doubt we’d find many examples in songs of this note played over a G major chord.
Take a listen for yourself:
Go ahead and play along with the MP3 and see which notes sound good to you. Have a great day!
Peace~
Dave
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