  In this short report, a new Lyapunov function for the Moog voltage-controlled
filter is demonstrated, under zero-input conditions, and under nonlinear
autonomous conditions (i.e. when parameters are not time-varying). The new
definition allows for a proof of stability over the entire allowable range of
parameters (cutoff frequency and resonance), and can be used as a starting
point for Hamiltonian-based numerical simulation methods.
