The linear propagation of magnetosonic and of shear Alfven waves is considered in a magnetic configuration with an X-line and a parallel (along the X-line) magnetic field B/sup ///. The two modes are decoupled both in the limits of zero and of infinite B/sup ///, whereas for finite B/sup /// they transform one into the other. The spatial structure of the current densities induced by this transformation is examined in the small and in the large B/sup /// limit. In both limits the induced currents exhibit, either at the separatrices or at the X-line, singular structures which can be associated with the formation of current sheets.