“We might add that to sing without accompani-ment the (equally) tempered scale is an under-taking beyond human capacities, because we cannot, without strong external help, escape from harmonic intervals (JI) , which alone are in accord-ance with the physical nature of sound and con-sequently with the shapes and possibilities of the organs by which we can emit and perceive them.”

(Danielou, Music and the Power of Sound - Rochester 1943)