Why does Salieri address the audience in the play, Amadeus?

Salieri often addresses the audience to gain their support and understanding as the scenes shift back to the play's present. At the beginning of the play, when Salieri asks the members of the audience to be visible to him, the house lights go up so he can see them. He then tells them he is at their service and that he wants them to be his confessors. At the play's end, he warns the audience that they also will feel "the dreadful bite" of their failures, and when they do, Salieri as Patron Saint of Mediocrities will absolve them.