Let G be a compact Abelian
group with character group X. A standard characterization of Sidonicity of a subset
P of X is given by the statement: if f ∈ C(G) and the Fourier transform f vanishes
on X|P, then ∑χ ∈ X|f(χ)| < ∞. In this paper, we show that the characterization
remains intact if C(G) is replaced by any one of a large class of smaller
function spaces on G. Extensions to compact non-Abelian groups are also
given.