The use of symbolic techniques to store integer-valued functions has been shown to be extremely effective in handling both transform matrices and spectral representations of large Boolean functions. In this paper we propose a novel application of symbolic Rademacher-Walsh spectral transforms to the evaluation of Boolean function correlation. In particular, we present an ADD-based algorithm to compute the agreement between two Boolean functions starting from their spectral representations. The method, operating in the transform domain, has appeared to be more advantageous than traditional approaches, using operations in the Boolean domain, concerning both memory occupation and execution time on some classes of functions.