  We present the wave equation for a minimally coupled scalar field in the
background of a rotating four-dimensional black hole that is parametrized by
its mass, angular momentum, and four independent U(1) charges. The near horizon
structure is identical to the five-dimensional case, and suggestive of an
underlying description in string theory that is valid in the general
non-extremal case. We calculate the greybody factors for the Hawking radiation.
For sufficiently large partial wave number the emission spectrum can be
calculated for general non-extremal black holes and any particle energy. We
interpret this spectrum in terms of a multi-body process in an effective string
theory.
