In 1755 a small vocal instruction book dedicated to the King’s mistress, Madame de Pompadour, was published in Paris under the name of [Jean-Antoine] Bérard. His role in this work was challenged a year later by l’abbé Jean Blanchet, who published a greatly enlarged version of Bérard’s book, claiming that he was its true author. Up to now, the lack of definitive source material has prevented a resolution of this question. New evidence clarifies its puzzling aspects, enabling us to reach a plausible conclusion. Investigating this matter leads also to insights in other areas, including the original meaning of the term amateur, the first known presentation of diaphragm breathing in print, the quality of singing at the Paris Opéra, contemporary views on the overuse of embellishment and audience behaviour.