`I recommend a critical review of the score sample from ``Trio en chaconne``. If you compare it with the edition in WIMA you'll notice the initial motive in WIMA's edition has the notes   4g | 2d+ 8a 16g 16a | 2b  in the right hand upper part while the sample in the Wikipedia article has  4g | 2c+ 8a 16g 16a | 2b  Unfortunately I've not access to the original printing of ``Livre d'Orgue``. But from a music analysis point of view it seems obvious that the leading motive spans the chord on the first degree of the key in use (in practice g-minor). The 2c+ found in the Wikipedia sample seems most unlikely to me.   `