Lattice dynamics is a classic part of solid state physics and the alkali halide crystals are classic materials. Nearly every new technique in many-body theory has first been applied to lattice-dynamical prob lems, and much of our present understanding of the physics of real crystals has its origins in pioneering work, both experimental and theoretical, carried out between 1920 and 1950 on alkali halide systems. The object of the present text is to present a unified coverage of that part of physics where these two areas overlap and to extend this coverage somewhat in order to include not...