  In this note we extend the spectral theorem for bimodules to the higher rank
graph C*-algebra context. Under the assumption that the graph is row finite and
has no sources, we show that a bimodule over a natural abelian subalgebra is
determined by its spectrum iff it is generated by the Cuntz-Krieger partial
isometries which it contains iff the bimodule is invariant under the gauge
automorphisms. We also show that the natural abelian subalgebra is a masa iff
the higher rank graph satisfies an aperiodicity condition.
