In a manuscript recently discovered in the Regensburg library of the princely family Thurn und Taxis, a courante in D-minor appears as nr. 51 which is identical to nr. 41 in Gustavson’s edition of the Bauyn MS. The piece is traditionally attributed to Louis Couperin, but since the appearance in the Early Keyboard Journal (edited by John Koster) of my article “The Other Mr. Couperin” (nr. 1 on this site), that is no longer tenable. The piece is in the highly advanced style of Louis’ younger brother Charles, and very different from the three courantes in G which are most likely indeed by Louis.*
The mostly retrospective Regensburg MS can hardly be dated earlier than 1701, since that is the date a Polonaise by Marais, which is included there in the same layer as the courante, first appeared. The courante in question is ascribed to “le vieux Couprin”. Since François was well-established by 1701, “le vieux Couprin” would be his father. This is one more proof that the pieces attributed to Louis in the past are in fact by Charles.
*The courante in the Regensburg MS is accompanied by an elaborate, unfinished double not found elsewhere, which bears no resemblace to anything from the generation of Couperins before François “le Grand”, Charles’ son; in fact, the closest thing to it are the agréments in pieces from François’ Première Ordre.