This fifth volume of Henry Du Mont’s Grands Motets brings together Super flumina, Ecce iste venit, Exaltabo te Deus meus, and finally the very beautiful Cantique de la Gloire Éternelle, composed to a neo-Latin poem by Pierre Perrin (1620–1675). In his introduction, Jean Duron, the scholarly editor of this volume, highlights a number of gaps in the inner orchestral parts (the hautes-contre and tailles de violon). While these parts do appear in the Ballard editions of 1686, they contain errors in counterpoint that cannot reasonably be attributed to Henry Du Mont himself. Based on this observation, and drawing on an analytical study of all 26 of the composer’s grands motets, Jean Duron suggests that these parts may have been added by an arranger employed by the publisher, since Du Mont had died prior to their publication. This hypothesis is also supported by a remark from Sébastien de Brossard, a contemporary of Henry Du Mont, who advised performers to play these grands motets with an ensemble of just five soloists, two violins, and a continuo. In fact, when this smaller scoring is applied to the grands motets, the writing proves to be flawless. A dual edition is therefore planned: this critical edition of the grands motets in the form passed down to us by Ballard, and a forthcoming “laboratory notebook” series presenting a restored version of two of these works.