We present a heavy quark description of quarkonium states and an effective lagrangian describing those interactions with chiral bosons and photons which occur in a soft-exchange-approximation regime. The formalism is expected to be valid for an intermediate heavy quark mass (up to ≈ 80 GeV) and is based on the approximate validity of the heavy quark spin symmetry and velocity superselection rule. Some applications to radiative and hadronic transitions are discussed.