This study focuses on the literary description of music. In the 15th chapter of Gustave Flaubert's Madame Bovary, the Bovarys go to the opera house in Rouen to listen to Donizetti's Lucie de Lammermoor. At first sight, the text presents a debased view of opera. However, behind the satire, we are made to discover Flaubert's own opinion about music and the literary means at his disposal to try to describe music, especially the ecphrasis and the "mise en abyme". Mr and Mrs Bovary's attitude must then be set back into the context of the aesthetic debate of the 19th century, led by the musicologist Edouard Hanslick, and dealing with the expression of emotions and the various functions of the musical language.