Below circuit is an echo chamber circuit which can be used for smoothing your voice from the microphone. This circuit may used for any kind of audio signal (microphone, radio, mp3 player, etc). The echo chamber circuit is great for human voice (karaoke), i doesn’t needed for music sound.
This circuit is quite complex with some number of components used to build it. 12V DC power supply is used to operate this circuit. Adjust the potensiometer to get echo level you need.
An echo chamber (echo repeater) is a hollow enclosure used to produce echoing sounds, usually for recording purposes. For example, the producers of a television or radio program might wish to produce the aural illusion that a conversation is taking place in a cave; this effect might be accomplished by playing the recording of the conversation inside an echo chamber, with an accompanying microphone to catch the echoes.
echo chamber/echo repeater circuit diagram source: schematic-diagram.com