This article—part of a Common Knowledge symposium titled “Between Text and Performance”—argues that the publication of a new edition of Il barbiere di Siviglia in Works of Gioachino Rossini (Bärenreiter-Verlag, Kassel) offers an excellent opportunity to reflect upon the written text of an opera and its relationship to the work that performers must do to realize the opera in the theater. Rossini wrote many passages that demand the intervention of performers (performing them “as written” is simply an error), yet this does not mean necessarily that “anything goes.” The new edition not only gives Rossini's own variations for the opera, but also (in an appendix prepared by Will Crutchfield) indicates the nature of ornamentation and variations employed by singers before 1850. Many of the variations still heard today in the opera house reflect practices from the end of the nineteenth and early twentieth centuries. There is no moral obligation to avoid such practices, but one wants singers to be fully aware of what they are doing. This essay provides extensive examples of the kind of autograph notation that signals the obligatory intervention of performers and offers many examples from performers who were contemporaries of Rossini as to how they went about their task of representing the composer's work on stage.