Kalman filters have been employed very successfully in control and guidance systems since the sixties, with particular application to avionics and navigation. These filters can track accurately signals of known structure among noise and other signal components with different structure.This paper investigates the application of nonstationary Kalman filters to track harmonic components. This approach enables the analysis of harmonic components in signals even when the rate of change of frequency, or slew rate, is high.A Kalman filter formulation to track harmonic components in data records sampled with constant frequency is first reviewed. Particular attention is paid to the characteristics of the filters in terms of filter resolution and harmonic separation, as well as ability to handle higher slew rates. The applicability of the method is demonstrated for analyzing driveline harshness problem.