Ça Ira is the fourth studio album by Roger Waters. It is an opera in three acts and a concept album. The album is based on the French libretto co-written by Étienne and Nadine Roda-Gil on the historical subject of the early French Revolution. Ça Ira was released 26 September 2005, as a double CD album featuring baritone Bryn Terfel, soprano Ying Huang, and tenor Paul Groves. The album received mixed reviews, with critics praising the composition but criticising its plot and simplicity.