  Potential-density pair basis sets can be used for highly efficient N-body
simulation codes, but they suffer from a lack of versatility, i.e. a basis set
has to be constructed for each different class of stellar system. We present
numerical techniques for generating a biorthonormal potential-density pair
basis set which has a general specified pair as its lowest order member. We go
on to demonstrate how the set can be used to construct N-body equilibria, which
we then evolve using an N-body code which calculates forces using the basis
set.
