  We propose ultranarrow dynamical control of population oscillation (PO)
between ground states through the polarization content of an input bichromatic
field. Appropriate engineering of classical interference between optical fields
results in PO arising exclusively from optical pumping. Contrary to the
expected broad spectral response associated with optical pumping, we obtain
subnatural linewidth in complete absence of quantum interference. The
ellipticity of the light polarizations can be used for temporal shaping of the
PO leading to generation of multiple sidebands even at low light level.
