Wave propagation through an assembly of spheres I. The Greenian method of the theory of metals

`The Green function method' proposed by Phariseau and Ziman (1963) for the calculation of the electronic structure of liquid metals is shown to be a powerful general solution of the well-known problem of the propagation of wave-like excitations (acoustic, electromagnetic, etc.) through a disordered assembly of non-overlapping spherical scatterers. The heuristic `Bloch' assumption of the PZ theory is rederived as a simple consequence of the standard `coherent wave approximation' originally suggested by Foldy in 1945, where the wave function on each sphere depends only on its position in space, and on the average arrangement of the other spheres (e.g. through the radial distribution function g(x)).