  We explore a series expansion method to calculate the modes of oscillations
for a variety of uniformly rotating finite disks, either with or without a dark
halo. Since all models have the same potential, this survey focuses on the role
of the distribution function in stability analyses. We show that the stability
behaviour is greatly influenced by the structure of the unperturbed
distribution, particularly by its energy dependence. In addition we find that
uniformly rotating disks with a halo in general can feature spiral-like
instabilities.
