The term voice changer (also known as voice enhancer) refers to a system of altering a person's voice to either make them sound like someone else or to disguise their voice.
Voice changers change the tone or pitch, add distortion to the user's voice, or a combination of all of the above and vary greatly in price and sophistication. A kazoo/didgeridoo can be used as a makeshift voice changer, though it can be difficult to understand what the person is trying to say.
The earliest voice changers were electronic devices usually used over the telephone for the purpose of disguise. There are low-priced, small lithium battery-powered voice changers that are used between a phone's mouthpiece and the user's mouth. More sophisticated voice changers have different levels of various distortion effects variable by faders.
Voice changers can be found online, for a variety of operating systems. There are several popular types of voice changers. The available programs are capable of altering the pitch and timbre of the user's voice, applying special effects, and performing graphic equalization almost in real-time.