  We study the L-functions associated to Siegel modular forms (equivalently,
automorphic representations of ${\rm GSp}(4,\mathbb{A}_{\mathbb{Q}})$) both
theoretically and numerically. For the L-functions of degrees 10, 14, and 16 we
perform representation theoretic calculations to cast the Langlands L-function
in classical terms. We develop a precise notion of what it means to test a
conjectured functional equation for an L-function, and we apply this to the
degree 10 adjoint L-function associated to a Siegel modular form.
