9.7Why the fifth is often omitted
The fifth usually contributes less information about chord quality than:
- root
- 3rd
- 7th
For example:
G B F
already tells us:
- G root
- B = major 3rd
- F = minor 7th
That strongly says:
G7
D is not necessary.
This becomes important when we add 9ths, 11ths, and 13ths later.