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 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.