A general approach to the light-induced anisotropy (LIA) effects in initially isotropic media subjected to a biharmonic laser field (pump-probe), that is based on a tensor operator formalism, is presented. Using such a theoretical treatment, we propose novel nonlinear spectroscopic techniques. We show new results dealing with advantageous measurement of the 3rd-order nondegenerate nonlinear susceptibility (3NNS), including the 3NNS phase (3NNSP) and the real and imaginary parts of the effective 3NNS. Figure 1 is the schematic illustration of a method for measuring 3NNSP in the framework of optically heterodyned polarization spectroscopy (OHPS) when the components of 3NNS are connected by the Kleinman relationships. In the standard OHPS arrangement with the slightly tilted analyzer and the linearly polarized probe beam at 45 to the major axis of the pump polarization ellipse, under tuning of the …