Ventriloquism is a form of entertainment where a person seems to cause their voice to emanate from another object. Ventriloquism is an illusion since it is absolutely impossible to change the origin of your voice through any analog methods. As with many illusions, however, ventriloquism is a popular form of entertainment.
There are two forms of ventriloquism. Near ventriloquism, which is most popular in the modern era, is when ventriloquists make it appear that their voice is originating from something nearby, such as a dummy. Distant ventriloquism, which many do not consider to be "true" is when the voice originates from some unseen location, but appears to originate from an object.
As previously mentioned, the ventriloquist does not actually change the origin of his or her voice. Practitioners of ventriloquism are skilled at speaking without moving their lips or jaw. By manipulating another object, often a dummy, the ventriloquist makes it appear that the sound is coming from that source. This is caused by two conflicting senses. Our eyes notice that the ventriloquist is not moving his mouth, yet we still hear the sound. When we see that the dummy's mouth is moving, our brain makes the connection that the sound must be coming from the dummy.
There are certain sounds that must be sacrificed in order to effectively perform ventriloquism. Sounds such as m, b, and p must be replaced with similar sounding consonants, since they cannot be made without lip-to-lip contact. If a ventriloquist replaces, say, the "m" in made with a "d," and if it is spoken quickly enough, the audience should not be able to tell the difference.
Ventriloquism dates back as early as ancient Greece, where it was often associated with magic. During the Middle Ages, performing ventriloquism was often considered a form of witchcraft, complete with all the punishments. The modern form of ventriloquism did not emerge until the 16th century when it was accepted as a form of entertainment and not as magic which should be feared.
Ventriloquism got its big break during the American Vaudeville era. During this time period, numerous ventriloquists paved the way for modern performers. Famous ventriloquists of note include, but are not limited to, Jules Vernon, Edward Berger, and The Great Lester. Although many of these individuals used multiple dummies in their act, it was The Great Lester who made single dummy ventriloquism acts popular.