  We have explored spectral line profiles due to spiral patterns in accretion
discs around black holes. A parametrization was employed for the shape and
emissivity of spiral waves, which can be produced by non-axisymmetric
perturbations affecting the disc density and ionization structure. The effects
of the light-travel time, energy shift, and gravitational focusing near to a
rotating black hole were taken into account. A high-resolution ray-tracing code
was used to follow the time variations of the synthetic line profile. A variety
of expected spectral features were examined and the scheme applied to a broad
iron line observed in MCG-6-30-15.
