Inelastic neutron scattering experiments on Nd2BaNiO5 single crystals and powder samples are used to study the dynamic coupling of one-dimensional Haldane-gap excitations in the S=1 Ni2+-chains to local crystal-field transitions, associated with the rare earth ions. Substantial interference between the two types of excitations is observed even in the one-dimensional paramagnetic phase. Despite that, the results provide solid justification for the previously proposed "static staggered field" model for R2BaNiO5 nickelates. The observed behavior is qualitatively explained by a simple chain-random-phase-approximation model.