Although this kind of voice effect can be obtained by means of some audio computer programs, depending on the equipment you are using this microphone input and loudspeaker output could be more versatile.
This design uses a variable gain microphone preamplifier built around IC1A, a variable steep Wien-bridge pass-band filter centered at about 1KHz provided by IC1B and an audio amplifier chip (IC2) driving the loudspeaker.
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