  We apply the confluent Heun functions to study the resonant frequencies
(quasispectrum), the Hawking radiation and the scattering process of scalar
waves, in a class of spacetimes, namely, the ones generated by a
Kerr-Newman-Kasuya spacetime (dyon black hole) and a Reissner-Nordstr\"{o}m
black hole surrounded by a magnetic field (Ernst spacetime). In both
spacetimes, the solutions for the angular and radial parts of the corresponding
Klein-Gordon equations are obtained exactly, for massive and massless fields,
respectively. The special cases of Kerr and Schwarzschild black holes are
analyzed and the solutions obtained, as well as in the case of a Schwarzschild
black hole surrounded by a magnetic field. In all these special situations, the
resonant frequencies, Hawking radiation and scattering are studied.

General Relativity and Quantum Cosmology