Spatial spin-resonance for the monochromatization or spectrum shaping of polarized neutrons is investigated in a system of mutually perpendicular magnetic fields: a constant guiding magnetic field and a static periodic magnetic field whose spatial periodicity is modulated. It is shown that the period modulation of the spatially alternating field as well as the modulation of the guiding magnetic field allows a change in the resonator line-width over a wide range. The harmonic approach to the modulation of an effective magnetic field is considered in a reference frame connected with the neutron. A comparative analysis as well as computer simulation are performed for the spectra obtained by means of different modulation methods.