The Préludes non mesurés formerly attributed to Louis Couperin, and now attributed by the present editor in large part to his brother Charles (more details in the Early Keyboard Journal in the download section), the father of François “le Grand”, are some of the finest keyboard works of the 17th century. The major problem confronting an editor here is the fact that the autographs have been lost. Copyists of the Couperins’ day and the editors who based themselves on their copies were unable to reproduce these pieces in a musically consistent and satisfying way. The metrically free, non mesuré notation and the imprecise length of the held notes (“tenues”) present problems that are difficult to solve. They call for the style-critical competence of a Glen Wilson, who elucidates his decisions in a preface and confirms his own experience as an interpreter of these works in the music files we present for free download, which offer one of an infinite number of possible interpretations of the Préludes.