This paper is devoted to the analysis of effective electromechanical properties and their maxima in 0–3-type composites based on (1 − x)Pb(Mg1/3Nb2/3)O3 − xPbTiO3 single crystals. It is shown that the electromechanical interaction between the single-crystal and polymer components with the anisotropy of their piezoelectric coefficients e33 /|e31 | ≥ 5 results in relations d33* ≈ e33*s33*, g33* ≈ h33*s33*, and kt* ≈ k33* for the electromechanical constants. These relations hold in a wide range of volume fraction and aspect ratio of the spheroidal inclusions in the 0–3 composite. An increase in the maximum values of different effective parameters is expected by forming a system of oblate air pores in the matrix.