George Moore involved W. B. Yeats personally in the revision of a novel of Moore's that contained a character based on Yeats; this involvement led to the pair's collaboration in writing a play based on Diarmuid and Grania, one of the best-known tragic tales of Celtic mythology. At the late stages of composition, the authors decided to add songs, and Edward Elgar provided the music. The play opened at the Gaiety Theatre in Dublin on October 21, 1901. Although the collaboration had been difficult-Yeats and Moore disagreed frequently, mainly about style-the production was well received. Controversy arose, however, because English actors played these most Irish of characters. After the play was produced, Yeats, whose commitment had occasionally seemed to waver, defended it against all criticism. The manuscript materials included in the Cornell Yeats edition of Diarmuid and Grania provide a full record of the disputes and revisions that culminated in the final draft. In his Introduction, J. C. C. Mays writes, "If one looks beyond words or passages that can be tagged with an author's name and a specific date, one can see signatures of each author no less clearly than such tags afford and perhaps see each writer more pervasively inhabiting the characters and situations of the play."