Apart from the overture, the most famous piece in the opera is the tenor's aubade in act 3, "Vainement, ma bien-aimée" ("In vain, my beloved").

His interest in the folklore of Brittany was prompted by his wife, the contralto Julie de Maligny, who was of Breton origin.

[5] Lalo undertook a revision of the work in 1886, and it was finally premiered by the Opéra-Comique in the Salle du Châtelet, Paris, on 7 May 1888 to great success.

The opera also enjoyed considerable success in Europe, with first performances in Geneva in November 1888, Amsterdam in December 1888, Antwerp and Brussels in February 1889, and Rome in March 1890.

The Metropolitan premiere starred Rosa Ponselle as Margared, Beniamino Gigli as Mylio, and Frances Alda as Rozenn.

One of the most recent fully staged versions was the October 2007 production at the Théâtre du Capitole, Toulouse, directed by Nicolas Joël and conducted by Yves Abel with Sophie Koch, Inva Mula, Charles Castronovo, Franck Ferrari and Paul Gay in the leading roles.

[13] As part of a peace agreement, Margared, the daughter of the King of Ys, is betrothed to Prince Karnac, a former enemy of the city.

The statue of St Corentin warns her to repent, but she ignores him and plans to give Karnac the keys to the sluice gates that protect the city from the sea.

Margared, stricken with remorse, tells them that the ocean demands a sacrifice and hurls herself into the sea from a high rock.

"[14] A more recent recording of the overture by Yan Pascal Tortelier and the BBC Philharmonic, which was included on a Chandos CD with Lalo's Violin Concerto, was also given high praise by the 2008 Gramophone Classical Music Guide as "certainly the finest account since Paray's old Mercury version.