  Let G be a discrete group and $\Gamma$ an almost normal subgroup. The
operation of cosets concatanation extended by linearity gives rise to an
operator system that is embeddable in a natural C* algebra. The Hecke algebra
naturally embeds as a diagonal of the tensor product of this algebra with its
opposite. When represented on the $l^2$ space of the group, by left and right
convolution operators, this representation gives rise to abstract Hecke
operators that in the modular group case, are unitarily equivalent to the
classical operators on Maass wave forms
