  The mean field Kuramoto model describing the synchronization of a population
of phase oscillators with a bimodal frequency distribution is analyzed (by the
method of multiple scales) near regions in its phase diagram corresponding to
synchronization to phases with a time periodic order parameter. The richest
behavior is found near the tricritical point were the incoherent, stationarily
synchronized, ``traveling wave'' and ``standing wave'' phases coexist. The
behavior near the tricritical point can be extrapolated to the rest of the
phase diagram. Direct Brownian simulation of the model confirms our findings.
