(I learned this a half century ago at the Sloan School, and there are diluted forms of it from consultants all over the Internet, none as concise as I would like)
Management can learn lessons from bands and orchestras. These lessons should be obvious to the casual observer. If not, their proof is left as an exercise to the reader. (Yes, I know I am not Fermat)
I play tenor sax in the Danville Band. We have one conductor (Bob Calonico) with a span of control of 80. Modern management theory says a manager should have no more than six reports, and yet our band does not have 3 subconductors and 15 sub-subconductors. Why is that?
We are all playing from the same music and we are all (theoretically) competent at our jobs.