1. An apparatus for optically and electrically stimulating neural tissue in a cochlea of a person, the cochlea having a length between a basal end of the cochlea and an apical end of the cochlea, in order to trigger compound nerve action potentials (CNAPs) that evoke auditory sensations for the person, wherein the cochlea has a modiolus that forms a central axis of the cochlea, the apparatus comprising: means for delivering pulsed optical-stimulation signals to a plurality of different frequency-response locations along the length of the cochlea from a first frequency-response location that is closer to the basal end of the cochlea than to the apical end of the cochlea to a second frequency-response location that is closer to the apical end of the cochlea than is the first frequency-response location; and means for delivering pulsed electrical-stimulation signals to one or more frequency-response locations in the cochlea of the person that are each closer to the apical end of the cochlea than is the second frequency-response location such that the delivered electrical-stimulation signals stimulate apical spiral ganglion cells in frequency-response locations associated with sensations of audio frequencies of less than 250 Hz, wherein the means for delivering pulsed electrical-stimulation signals includes a signal electrode adapted to be located on a first side of the modiolus of the cochlea and a return electrode configured to provide an electrical ground for return current, wherein the return electrode is adapted to be located on a side opposite the first side of the modiolus of the cochlea, and wherein the signal electrode and the return electrode are configured to provide an electric field that extends across at least a first auditory nerve of the cochlea between the signal electrode and the return electrode, the signal electrode and the return electrode extending distally beyond the optical guide and one of the signal electrode and the return electrode extending distally beyond the other.