Modern electric field-based spectroscopies, both linear and nonlinear, are assigned to two classes having strongly differentiating properties. In one, Class I, the language of photons absorbed and emitted appears naturally. In Class II, the basic physics is sorted out at the field level itself and the language of wave-mixing is used. So, among other things, the phase of the material response function becomes an issue for Class II spectroscopies. Field "generators" together with density matrix evolution diagrams are found to be useful tools for isolating any given spectroscopy from the great many that may appear at any given order in the light-matter interaction. By way of example, it is shown how the generators and diagrams allow one to extract all of the Raman scattering processes as a distinct subgroup of a much larger set of spectroscopies that occur at various orders. Each is assigned either to Class I or II and identified with key evolution diagrams.