The electromechanical device of FIG. 4, used in this discussion, is a member of a large class of electromechanical filters with nonlinear input transducers, other examples of which are shown in FIGS. 6 and 8A-8B. The serpentine ring torsional structure 63 of FIG. 6 is disclosed in above-mentioned U.S. Pat. No. 5,025,346 dated Jun. 18, 1991.