Dramatic voice is the method by which a writer creates the illusion that the reader or viewer is eavesdropping on a series of events that would be happening whether she was there or not. It is differentiated from narrative voice, wherein the writer describes what is going on by means of an omniscient narrator who may make judgments about the characters and events. With dramatic voice, the reader gains only information that would be available to the characters and must make her own judgements based on that.
Strict adherence to dramatic voice limits how much of the author's voice comes through in the finished work. While this is not a large problem in stories or films that embrace realism, it can restrict the writer's expression in poetry and experimental fiction, preventing the presentation of a unified, lyrical voice throughout the piece. Because dramatic voice relies on the reader to make his own judgements about what is happening, it opens the work to multiple interpretations.
Though dramatic voice is contrasted with narrative voice, there is some overlap. At the deepest level, all voice in a written work is narrative voice because the writer is still the one creating it -- the words are still his. Dramatic voice may be better understood as a way of masking narrative voice from the audience by making it look like something that is happening in the real world to real people. In some cases, a single character may become a mouthpiece for narrative voice that is only thinly veiled.
Dramatic voice comes into play in scriptwriting, story writing and poetry. In film, the writer shares the burden of dramatic voice with the director, who may influence it through camera work. In novels and short stories, dramatic voice comes from the way scenes are set, allowing characters to respond naturally to the action dreamed up by the writer. Poets, when they include dramatic voice at all, can influence it through the use of quotes and different points of view within the poem.