  A short analysis is presented of the effects on the cepheid light curve
shape, i.e. on the Fourier parameters usually adopted for its description, of
the blending of the stellar image with other close stars. The conclusion is
that, within reasonable error, the effects are in general small and the Fourier
decomposition is confirmed to be a useful tool for pulsation mode
discrimination. A large effect has been found on the phase differences in a
narrow period range corresponding to the known resonance centers between
pulsation modes.
