Louis was evidently a very successful and influential composer, but he died young, in 1661, and most of his compositions remained unpublished until the 20th century. Some years after his death, the second of the two most important Couperins was born: François Couperin, nicknamed "le Grand"—"the Great". Although suffering from poor health throughout his life, François was a very prolific composer. He produced four "livres" of harpsichord pieces that represent the summit of the French harpsichord school, authored an influential and historically important treatise on harpsichord playing ("L'art de toucher le clavecin"), and produced a number of other, sacred and secular works, that are still well known today.