  The near-horizon geometry of parallel NS5-branes is described by an exact
superconformal 2d field theory based on K^10 = W(k)^4 x M^6, with M^6 a flat
5+1 space time and W(k)^4 =U(1) x SU(2)(k), a four dimensional background with
non-trivial dilaton. The ten-dimensional ``BULK'' spectrum of excitations of
K^10 can be derived combining unitary representations of the N=4 superconformal
theory of W(k)^4 and M^6 in a modular-invariant way. All Bulk states are
massive and belong to the long representations of the N=2 six dimensional
space-time supersymmetry. The NS5-brane states, propagating on M^6, belong to
the short representations of N=2. Both the bulk and the brane spectrum is
derived using the powerful worldsheet technics of the N=4 superconformal
theories. We claim that both bulk and brane states are necessary to well define
the theory. The non abelian U(n) or SO(2n) structure of the 5-brane fields
follows from the fusion coefficients appearing in the correlation functions
involving SU(2)(k) conformal fields.
