A compressor apparatus includes: a rotor (38) including: a disk (40) mounted for rotation about a centerline axis (11), an outer periphery of the disk defining a flowpath surface (50) having an non-axisymmetric surface profile; an array of airfoil-shaped axial-flow compressor blades (52) extending radially outward from the flowpath surface, wherein the compressor blades each have a root, a tip, a leading edge, and a trailing edge; and an array of airfoil-shaped splitter blades (152) alternating with the compressor blades, wherein the splitter blades each have a root, a tip, a leading edge, and a trailing edge; and wherein at least one of a chord dimension of the splitter blades at the roots thereof and a span dimension of the splitter blades is less than the corresponding dimension of the compressor blades.