  Motivated by puzzling results of recent experiments, we re-examine the
response of a weakly pinned two-dimensional Wigner crystal to a uniform AC
electric field. We confirm that at some disorder and magnetic field dependent
frequency $\omega_p$, an inhomogeneously broadened absorption line emerges.
Although the line is conventionally broad in zero magnetic field, in strong
fields it appears as a sharp resonance whose width is related to the density of
states in the low-frequency tail of the zero-field phonon spectrum. This
behavior originates due to the long-range Coulomb interactions.
