The coherent potential approximation has been generalized to incorporate the effects of the local environment in the energy spectrum of disordered alloys described by the simple tight-binding approximation. The effective medium has been characterized by an effective local potential Sigma 1 and an effective hopping integral Sigma 2 between the nearest neighbours though the off-diagonal elements of the alloy Hamiltonian are not assumed to be disordered in the present calculation. The density of states has been calculated for a binary alloy AxB1-x having diamond lattice structure.