  Brown-Rho scaling, which has been strongly discussed after recent NA60 data
was presented, is investigated within a nonequilibrium field theoretical
description that includes quantum mechanical memory. Dimuon yields are
calculated by application of a model for the fireball, and strong modifications
are found in the comparison to quasi-equilibrium calculations, which assume
instantaneous adjustment of all meson properties to the surrounding medium. In
addition, we show results for the situation of very broad excitations.
