Abstract. In this paper we offer a computational approach to the spectral function for a finite family of commuting operators, and give applications. Motivated by questions in wavelets and in signal processing, we study a problem about spectral concentration of integral translations of functions in the Hilbert space L 2 (R n ). Our approach applies more generally to families of n arbitrary commuting unitary operators in a complex Hilbert space H, or equivalent the spectral theory of a unitary representation U of the rank-n lattice Z n in R n . Starting with a non-zero vector ψ ∈ H, we look for relations among the vectors in the cyclic subspace in H generated by ψ. Since these vectors {U (k)ψ|k ∈ Z n } involve infinite "linear combinations," the problem arises of giving geometric characterizations of these non-trivial linear relations. A special case of the problem arose initially in work of Kolmogorov under the name L 2 -independence. This refers to infinite linear combinations of integral translates of a fixed function with l 2 -coefficients. While we were motivated by the study of translation operators arising in wavelet and frame theory, we stress that our present results are general; our theorems are about spectral densities for general unitary operators, and for stochastic integrals.Mathematics Subject Classification (2000). Primary 47B40, 47B06, 06D22, 62M15; Secondary 42C40, 62M20.