Gathered from the indications of J.G. Walther, the registration of another chorale appears to bear the marks of more positive authenticity. We refer to the Lutheran chorale, _Ein' feste Burg ist unser Gott_, mentioned in a previous chapter. Walther thus annotates it: "Für 3 clav."; for the left hand he directs "_Fagotto_"; for the right, "_Sesquialtera_." First of all must we notice this combination of a mutation stop with a reed; it is derived directly from the French organists. In Grigny,[162] for instance--we cite him especially because of Bach's study of his works--may be found in various instances a Bass Trumpet, or _Cromorne en taille_, accompanied by the _Tierce_ or Cornet.[163] To a certain extent the _Fagotto_ corresponds to the _Cromorne_, whose tone appeared somewhat veiled. This register, which Adlung tells us bore various names--_Portunen_, _Dulcian_, or _Basson_, among others--was sometimes added to the lower half of the great organ only, and was "of good effect in playing the _basso continuo_." Moreover, it was of small scale; even on the pedal it was not a noisy stop. As for the _Sesquialtera_, composed of the fifth and the tenth, it resembled more or less certain mutation stops of old French organs. It is noteworthy that the employment of a reed with a mixture is not mentioned by contemporary German writers; on the other hand, it would seem from the context[164] that this piece was played at the inauguration of the Mühlhausen organ, for whose restoration Bach had prepared the plans. He had demanded, among other improvements, that a _Tierce_ be added to one of the manuals, in order that, by drawing it with a _Quint_, a good _Sesquialtera_ might be produced; this in order to carry out all sorts of musical inventions of his own. [Footnote 162: _Livre d'orgue contenant une messe et quatre hymnes pour les principales festes de l'année. Par Nicolas de Grigny, organiste de l'église-cathédrale de Reims. À Paris, chez Christophe Ballard, seul imprimeur du Roy pour la Musique. Rue Saint-Jean de Beauvais, au Mont-Parnasse. 1701. Avec Privilège de Sa Majesté._] [Footnote 163: [The cornet here referred to is obviously a mixture, not the reed of the same name already mentioned.--TR.]] [Footnote 164: This organ was the only one with three manuals which Bach could have had in mind while he was in Weimar with Walther; it is natural that in his compositions he should be preoccupied with an organ whose restoration he had planned, and undoubtedly supervised--Weimar being not far from Mühlhausen--and which in all probability he looked forward to inaugurating. This remark, moreover, may apply to the composition of the chorale _In dir ist Freude_, although here Bach had been disappointed.] It is interesting to learn the details of this project, which, it is true, was not realized in its integrity; and it furnishes us with the most curious data upon the subject of Bach's ideas on registration and organ-building, and his own tastes.