Abstract: This invention digitally simulates periodic frequency modulation, especially the use of fudge factors to reduce digitization error. The fudge factor is based upon the relationship of expected and actual results. The fudge factor is derived from data during previously completed periods and can be applied to upcoming periods of rotation. The frequency modulation can be applied by varying the step sizes during the simulation. This invention can be applied to simulate the frequency modulation of a rotating speaker. The digital apparatus that implements this invented process includes a digital processor and memory. In summary, this invention is much more stable and realistic sounding than prior-art.