  We give a new derivation of the quasinormal frequencies of Schwarzschild
black holes in d>=4 and Reissner-Nordstrom black holes in d=4, in the limit of
infinite damping. For Schwarzschild in d>=4 we find that the asymptotic real
part is T_Hawking.log(3) for scalar perturbations and for some gravitational
perturbations; this confirms a result previously obtained by other means in the
case d=4. For Reissner-Nordstrom in d=4 we find a specific generally aperiodic
behavior for the quasinormal frequencies, both for scalar perturbations and for
electromagnetic-gravitational perturbations. The formulae are obtained by
studying the monodromy of the perturbation analytically continued to the
complex plane; the analysis depends essentially on the behavior of the
potential in the "unphysical" region near the black hole singularity.
