Solving the 3-D elastodynamic equations using traditional boundary element methods (BEMs) is greatly hindered by the fully-populated nature of the BEM matrix. In a previous study limited to homogeneous media, we have established that the Fast Multipole (FM) method reduces the complexity of a 3-D elastodynamic BEM to N log N per GMRES iteration. Here, the methodology is extented to piecewise-homogeneous domains using a FM-accelerated multi-region BE-BE coupling. Numerical examples, and a simple preconditioning approach, are presented.