Langlands conjecturally associates to a discrete symplectic motive M of rank 2n over Q a cuspidal, generic, automorphic representation pi = pi(M) of the split orthogonal group SO(2n+1). Using some special properties of generic, local representations of SO(2n+1), we define a line in the representation pi, and hence a cusp form associated to M. This may be useful in testing the Langlands conjectures computationally.