What is the tone of a piece of literature determined by?

Tone and mood are two literary terms that often have the same meaning. In general they refer to the 'over-all' feeling that the story induces in the reader.

In more rigorous definitions the tone refers to 'the tone of voice' employed by the narrator of the story.

The tone of 'The Raven' by Edgar Allan Poe, is despairing

The tone of 'Harrison Bergeron' by Kurt Vonnegut jr. is tongue in cheek