Careful examination of the manuscript sources of the harpsichord pieces of the ancestors of Francois Couperin 'Le Grand' reveals that nowhere are these compositions indisputably attributed to one of the three brothers Louis, Francois and Charles, born in Chaumes-en-Brie in 1626, 1630 and 1638. In these sources, the signatures mention an enigmatic 'Monsieur Couperin'. The question of the authorship of all these compositions thus remains open. What is certain is that, for various reasons, Louis, who died in 1661, cannot under any circumstances be the composer of all the pieces in the corpus generally attributed to him. Which pieces can be restored to Charles and perhaps Francois, who died in 1679 and 1701 respectively? It is this riddle, worthy of a detective story, that this recording attempts to solve