  In this write-up we summarize main results of our recent analyses on the
mixing between transverse rho and a1 mesons in hot and/or dense matter. We show
that the axial-vector meson contributes significantly to the vector spectral
function in hot matter through the mixing. In dense baryonic matter, we include
a mixing through a set of omega rho a1 -type interactions. We show that a clear
enhancement of the vector spectral function appears below \sqrt{s}=m_\rho for
small three-momenta of the rho meson, and thus the vector spectrum exhibits
broadening.
