A system for analyzing waveforms consisting of mixtures of exponentially damped sine waves is described. The instrument generates a set of damped sine waves of variable amplitude, frequency, damping decrement, and phase. These waveforms are added and displayed on an oscilloscope. Their parameters can be adjusted to obtain a waveform which matches the curve to be analyzed. The component waveforms are then analyzed one at a time. The instrument has been used to analyze interferometer curves arising in the course of plasma wave experiments.