  We demonstrate, using a simple analytic model, that the presence of a massive
satellite can globally modify the structure and emission properties of an
accretion disc to which it is tidally coupled. We show, using two levels of
numerical approximation, that the analytic model gives reasonable results. The
results are applicable to two astrophysical situations. In the case of an
active galactic nucleus, we consider the case of a $\sim 10^3\Msun$ compact
companion to the central black-hole and show that it could modulate the emitted
spectrum on a timescale of $\sim10^5$ years. In the case of a T Tauri accretion
disc, a satellite such as a sub-dwarf or giant planet could modify the disc
spectral energy distribution over a substantial fraction of the T Tauri star
lifetime.
