1. A method of electrically stimulating a nonlinear biological system, the method comprising: transforming an input signal using a plurality of dynamic modes to generate a plurality of modal outputs, the dynamic modes being configured to provide a functional representation of the input and output properties of said nonlinear biological system, and each dynamic mode performing a unique transformation of the input signal; scaling and combining the modal outputs using a plurality of mixing functions; applying the scaled and combined modal outputs to a ring device in the form of an oscillator that generates rhythm output represented by amplitude and phase variables, said modal outputs modifying the dynamics of said ring device in a time-dependent manner to modify the rates of change of the amplitude and phase variables; mapping the amplitude and phase variables to an external observable variable to generate a physiologically-representative and observable output electrical stimulation signal; and stimulating said nonlinear biological system with said physiologically-representative and observable output electrical stimulation signal via an electromechanical interface.