A human operator's voice is artificially varied prior to transmission to a remote caller. In one example, the operator indicates target speech content (e.g., actual speech, pre-prepared text, manually entered text) to a speech processing facility, which enunciates the target speech content with an output voice that exhibits prescribed speech characteristics (e.g., accent, dialect, speed, vocabulary, word choice, male/female, timbre, speaker age, fictional character, speech particular to people of a particular geographic region or socioeconomic status or other grouping). Another example is an automated call processing system, where an output voice is selected for each incoming call and information is interactively presented to callers using the output voice selected for their respective calls. In another example, a speech processing facility intercepts the operator's speech, manipulates the waveform representing the operator's intercepted speech to add or remove prescribed characteristics, and transmits an enunciated output of the manipulated waveform to the caller.