Question: Who wrote the libretto in a Shakespeare play-based opera by a man who was later Director of the Conservatoire de Paris?

Context articles: Jean-Louis Petit
Ambroise Thomas
André Bloch (composer)
Thérèse Brenet
Pierre Bourque (saxophonist)
Hamlet (opera)
Lily Laskine
Bernard Jean
Jeanne Leleu
Jean-Louis Martinet

Jean-Louis Petit (born 20 August 1937) is a French composer, conductor and organist.
 He studied composition with Georges Moineau and organ with Arsène Muzerelle at the Conservatoire de Reims before he studied under Simone Plé-Caussade and Olivier Messiaen at the Conservatoire de Paris.
 He joined courses in conducting with Leon Barzin at the Schola Cantorum, Franco Ferrara in Venice, Igor Markevitch in Madrid, Monaco und Santiago, Chile and Pierre Boulez in Basel.
Charles Louis Ambroise Thomas (5 August 1811 – 12 February 1896) was a French composer, best known for his operas "Mignon" (1866) and "Hamlet" (1868, after Shakespeare) and as Director of the Conservatoire de Paris from 1871 till his death.
André Bloch (14 January 1873, in Wissembourg – 7 August 1960, in Paris) was a French composer and music educator.
 He studied with André Gedalge, Ernest Guiraud, and Jules Massenet at the Conservatoire de Paris.
 In 1893 he won the Prix de Rome for his cantata "Antigone" which used a text by Ferdinand Beissier.
 The prize enabled him to pursue further studies at the French Academy in Rome.
 In 1898 he joined the faculty of the Conservatoire de Paris as a professor of harmony.
 One of his notable pupils at that school was Jehan Alain.
 He later taught at American Conservatory in Fontainebleau.
 His private students included the composer Fernand Oubradous.
Thérèse Brenet (born 22 October 1935 in Paris, France) is a French composer.
 She studied at the Conservatoire de Reims and since 1954 the Conservatoire de Paris.
 Among her teachers were Maurice Duruflé, Henri Dutilleux, Darius Milhaud, and Jean Rivier.
 In 1965 she won the Prix de Rome for her "Les Visions prophétiques de Cassandre"; a prize which enabled her to pursue further studies at the French Academy in Rome.
 She went on to win the Halphen Prize for fugue and composition and won the Coplay Foundation of Chicago's composition prize.
 She is also an honorary member of the National Academy of History in Reims.
Pierre Bourque (born 27 January 1938-died 31 October 2014) is a Canadian saxophonist and music educator.
 Born in Plessisville, Quebec, Bourque attended the Collège de Lévis in his youth.
 While there he was a member of the Sainte-Cécile concert band from 1948 to 1955.
 In 1955 he entered the Conservatoire de musique du Québec à Québec (CMQQ) where he was a pupil of Maurice DeCelles.
 He transferred to the Conservatoire de Paris in France in 1958 where he was a pupil of Marcel Mule.
 He graduated from the conservatory in 1961 with a premier prix in saxophone performance.
Hamlet is a grand opera in five acts of 1868 by the French composer Ambroise Thomas, with a libretto by Michel Carré and Jules Barbier based on a French adaptation by Alexandre Dumas, père, and Paul Meurice of William Shakespeare's play "Hamlet".
Lily Laskine (31 August 1893 in Paris– 4 January 1988 in Paris) was one of the most prominent harpists of the twentieth century.
 Born Lily Aimée Laskine to Jewish parents in Paris, she studied at the Conservatoire de Paris with Alphonse Hasselmans and became a frequent performing partner of several distinguished French flautists, including Marcel Moyse and Jean-Pierre Rampal.
 Laskine also served as professor of harp at the Conservatoire de Paris from 1948 to 1958.
 She was awarded the Legion of Honour in 1958.
 She died in Paris.
Bernard Jean (born 21 September 1948, in Jonquière, Quebec) is a Canadian oboist, english horn player, conductor, and music educator.
 He has held principal oboist positions with several important Canadian orchestras, including the Quebec Symphony Orchestra and the Montreal Symphony Orchestra.
 In 1972 he co-founded the Quebec Woodwind Quintet; a group he played and recorded with for the next 15 years.
 In 1987 he founded the St Louis de France Ensemble, a group which he has conducted and recorded works by Caplet, Constant, Milhaud, and Patch.
 He has also performed as a soloist with the National Arts Centre Orchestra among other notable ensembles.
 A graduate of the Conservatoire de Paris and the Conservatoire de musique du Québec à Québec, he has taught on the music faculties of Laval University (1972-1975) and Conservatoire de musique du Québec à Montréal (1975-present).
Jeanne Leleu (29 December 1898 – 11 March 1979) was a French pianist and composer.
 She was born in Saint-Mihiel and entered the Conservatoire de Paris at the age of nine, where she studied with Marguerite Long, Georges Caussade, Alfred Cortot and Charles-Marie Widor.
 With Geneviève Durony, Leleu gave the premiere performance of Ravel's "Ma mère l'oye" in 1910.
 Ravel composed his "Prelude" for a Paris Conservatoire sight-reading competition in 1913 and Leleu won the prize.
 Her cantata "Beatrix" won the Prix de Rome in 1923.
 After completing her studies, Leleu took a position as professor at the Conservatoire.
 She died in Paris.
Jean-Louis Martinet (born 8 November 1912, Sainte-Bazeille,died 20 December 2010) is a French composer.
 He studied at the Schola Cantorum with Charles Koechlin and at the Conservatoire de Paris with Jean Roger-Ducasse and Olivier Messiaen.
 He also studied privately with René Leibowitz.
 In 1971 he was appointed professor at the Conservatoire de musique du Québec à Montréal.