Voice box (effects pedal)

A talk box or talkbox is an effects unit that allows musicians to modify the sound of a musical instrument by shaping the frequency content of the sound and to apply speech sounds (in the same way as singing) onto the sounds of the instrument. Typically, a talk box directs sound from the instrument into the musician's mouth by means of a plastic tube adjacent to their vocal microphone. The musician controls the modification of the instrument's sound by changing the shape of the mouth, "vocalizing" the instrument's output into a microphone.

A talk box is usually an effects pedal that sits on the floor and contains a speaker attached with an airtight connection to a plastic tube; however, it can come in other forms, including homemade, usually crude, versions, and higher quality custom-made versions. The speaker is generally in the form of a compression driver, the sound-generating part of a horn loudspeaker with the horn replaced by the tube connection.

The box has connectors for the connection to the speaker output of an instrument amplifier and a connection to a normal instrument speaker. A foot-operated switch on the box directs the sound either to the talk box speaker or to the normal speaker. The switch is usually a push-on/push-off type. The other end of the tube is taped to the side of a microphone, extending enough to direct the reproduced sound in or near the performer's mouth.

When activated, the sound from the amplifier is reproduced by the speaker in the talk box and directed through the tube into the performer's mouth. The shape of the mouth filters the sound, with the modified sound being picked up by the microphone. The shape of the mouth changes the harmonic content of the sound in the same way it affects the harmonic content generated by the vocal folds when speaking.

The performer can vary the shape of the mouth and position of the tongue, changing the sound of the instrument being reproduced by the talk box speaker. The performer can mouth words, with the resulting effect sounding as though the instrument is speaking. This "shaped" sound exits the performer's mouth, and when it enters a microphone, an instrument/voice hybrid is heard.

The sound can be that of any musical instrument, but the effect is most commonly associated with the guitar. The rich harmonics of an electric guitar are shaped by the mouth, producing a sound very similar to voice, effectively allowing the guitar to appear to "speak".

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