The opera Wagner Dream, by composer Jonathan Harvey, premiered in 2007. In this cahier, Harvey discusses with his librettist Jean-Claude Carrière the ideas underlying the opera and, in a detailed essay about the undecidability of music, reveals the opera’s Buddhist leitmotifs. With images from the opera and explanatory marginalia, this cahier offers a clear insight into the work of one of the foremost contemporary composers of electro-acoustic music.