  A generalization of Mallat's classic theory of multiresolution analysis based
on the theory of spectral pairs was considered by Gabardo and Nashed (J. Funct.
Anal. 158, 209-241, 1998). In this article, we introduce the notion of
biorthgonoal nonuniform multiresolution analysis on the spectrum
$\Lambda=\left\{0, r/N\right\}+2\mathbb Z$, where $N\ge 1$ is an integer and
$r$ is an odd integer with $1\le r\le 2N-1$ such that $r$ and $N$ are
relatively prime. We first establish the necessary and sufficient conditions
for the translates of a single function to form the Riesz bases for their
closed linear span. We provide the complete characterization for the
biorthogonality of the translates of scaling functions of two nonuniform
multiresolution analysis and the associated biorthogonal wavelet families.
Furthermore, under the mild assumptions on the scaling functions and the
corresponding wavelets associated with nonuniform multiresolution analysis, we
show that the wavelets can generate Reisz bases.
