The authors have extended the Kaiser-Teager algorithm for separating the contributions of the amplitude modulation and frequency modulation of a single sinusoid to a signal consisting of multiple components. An instantaneous nonlinear operator turns out to be the determinant of a Toeplitz matrix formed with the signal samples. Because of its instantaneously adaptive nature, this algorithm can be used to track parameter variations in the signal components, provided these variations are not too rapid. This is demonstrated using a synthetic signal containing two AM-FM components and a speech signal. The method's relationship to Prony's method is pointed out. © 1992 IEEE.