Background singers always come in threes.. Why is that?
Because, somehow, nature expresses harmony best in threes. The triangle is composed of three lines, a story has a beginning, a middle and an end, and even the golden rectangle is still divided in 3.
The smallest group can only be composed of 3 parts. Not two, otherwise that is a pair. A pair is symmetrical, but has no harmony. Try and look at a series of five and still not see a series of three.
This appears throughout nature, but the pattern is only recognized in our minds. It's how we organize infinity.
Why is this? I don’t know, but everytime I compose a shot, I make sure there’s relationships of threes.