A system and method for activating electrodes in an implanted electrode array with a stimulation signal is described. A stimulation definition stage, for each of a plurality of defined sound signal characteristics (C), assigns each electrode to one of a plurality of stimulation groups (G) each having an associated group stimulation amplitude function (A), where (G) varies with (C). An electrode stimulator activates each electrode as the stimulation signal varies based on spectral components of the stimulation signal.