We study Borel homomorphisms θ:G→H for arbitrary locally compact second countable groups G and H for which the measure
θ∗false(μfalse)false(αfalse)=μfalse(θ−1(α)false)forα⊆HaBorelsetis absolutely continuous with respect to ν, where μ (respectively, ν) is a Haar measure for G, (respectively, H). We define a natural mapping scriptG from the class of maximal abelian selfadjoint algebra bimodules (masa bimodules) in B(L2false(Hfalse)) into the class of masa bimodules in B(L2false(Gfalse)) and we use it to prove that if k⊆G×G is a set of operator synthesis, then (θ×θ)−1false(kfalse) is also a set of operator synthesis and if E⊆H is a set of local synthesis for the Fourier algebra A(H), then θ−1false(Efalse)⊆G is a set of local synthesis for A(G). We also prove that if θ−1false(Efalse) is an M‐set (respectively, M1‐set), then E is an M‐set (respectively, M1‐set) and if Bim(I⊥) is the masa bimodule generated by the annihilator of the ideal I in VN(G), then there exists an ideal J such that Gfalse(Bim(I⊥)false)=Bimfalse(J⊥false). If this ideal J is an ideal of multiplicity, then I is an ideal of multiplicity. In case θ∗false(μfalse) is a Haar measure for θ(G), we show that J is equal to the ideal ρ∗false(Ifalse) generated by ρ(I), where ρ(u)=u∘θ,∀u∈I.