  We have frequency analyzed 6391 variables classified earlier as fundamental
mode RR Lyrae (RR0) stars in the MACHO database on the Large Magellanic Cloud
(LMC). The overwhelming majority of these variables have been proved to be
indeed RR0 stars, whereas the remaining ones have fallen in one of the
following categories: single- and double-mode Cepheids, binaries, first
overtone and double-mode RR Lyrae stars and non-classified variables. Special
attention has been paid to the Blazhko stars. We found altogether 731 Blazhko
variables showing either a doublet or an equidistant triplet pattern at the
main pulsation component in their frequency spectra. The incidence rate of the
Blazhko variables among the RR0 stars in the LMC is 11.9%, which is three times
higher than their rate among the first overtone RR Lyrae stars. From the
frequency spectra we found that variables with larger modulation amplitudes at
the higher frequency side of the main pulsation component are three times more
frequent than the ones showing the opposite amplitude pattern. A search made
for a modulation component with the Blazhko period in the average brightness of
the individual variables showed the existence of such a modulation with an
overall amplitude of ~0.006 mag. On the other hand, a similar search for
quadruple modulation patterns around the main pulsation component have failed
to clearly detect such components at the ~0.004 mag level. This means that the
amplitudes of the quadruple components should be, on the average, at least ten
times smaller than those of the triplet components. This finding and the
existence of Blazhko variables with highly asymmetric modulation amplitudes not
only question the validity of the magnetic oblique rotator model, but also puts
stringent constraints on models based on mode coupling theories.
