1. A computer implemented method comprising: providing by a computer, a user interface that displays a plurality of representations of characters, the characters each including the representation as a graphic image of an entity corresponding to the character and at least one associated voice model, the voice model characterized by a set of attributes; receiving a user selection of one of the representations from the plurality of representations to associate with one or more portions of a sequence of words in an electronic document that is rendered on a user display device; associating by the computer the selected character corresponding to the representation with the selected one or more portions of the sequence of words; and modifying by the computer the at least one voice model associated with the selected character, with modifying applying data received from the user through the user interface to change one or more attributes of the set of attributes of the voice model.