ABSTRACT
It is known that Pythagoras, as long ago as the sixth century BC, exhibited a great interest in the laws of musical harmony as generated by the plucked strings of the lyre. The lyre usually consisted of a sounding board (often composed of a tortoise shell covered with bull's hide) from which curved horns extended in a U-shape to be connected near their tips by a wooden crosspiece. The Fourier transform method in solid state physics depends on the existence of a periodicity in the crystal structure. The immense value of this technique is brought home to physicists when they confront similar problems in glasses, for which the periodicity is not there. For these cases the equations of motion remain in the form of some 1024 variables all intertwined. Any property associated with the individual atoms in crystals must have this same structural periodicity which enables the Fourier method to be applied.
