Variation of (A) P- and (B) S-wave velocities with melt fraction for inclusions of aspect ratios a/c= 1 (spheres), 10 and 100 (thin discs) aligned with their c-axis in the 3 direction. The microstructure is that of melt added to a background solid matrix. Numbers along curves indicate aspect ratios. For anisotropic materials (a/c= 10 and 100), ‘horizontal’ (bold-dashed lines) and ‘vertical’ (narrow-solid and narrow-dashed lines) velocities are plotted. The sense of P- and S-wave directions and polarization, and the alignment of inclusions are indicated by the schematic diagram in the bottom left-hand corner.