When distinguished strangers asked to hear Bach at the organ, at times other than during services, he usually selected some theme and amused himself by treating it in various ways, perhaps playing without interruption for over an hour. First he made use of the subject for a prelude and fugue, upon the foundation stops of the chief manual, thereafter deftly varying his registration through a series of episodes in two, three, or four parts. Then came a chorale, the melody of which was interrupted here and there by fragments of the original subject; and he finally concluded with a fugue for full organ,[2] in which "he contented himself with treating the subject either alone, or in combination with other themes derived from it." [Footnote 2: See _organo pleno_, p. 70.] And if he tried a new organ? He first drew all the registers and played upon the principal manual (with all couplers), "in order to test the lung-power of the instrument," as he laughingly expressed it. Then he proceeded to a detailed inspection of every part of the organ. This expert examination once over, he gave free rein to his fancy. And now he showed himself truly "the prince of all _virtuosi_ of the universe, upon the harpsichord and organ," as he was one day hailed by his amazed colleague, the organist Sorge, of Lobenstein, in an outburst of enthusiasm. No, the art of organ playing has not changed since Johann Sebastian Bach; but, on the other hand, our organs are growing distinctly better. Go and listen to those of Saint-Sulpice, of Notre-Dame, in Paris; hear the instrument of Saint-Ouen, at Rouen! In the organs of Bach's time the reeds were scarcely used except in the capacity of basses, reinforcing the pedal; or as solo registers, for instance, _hautbois_ and _cromornes_; our profusion of sonorous clarions, trumpets, and _bombardes_ was totally unknown. _Organo pleno_ did not signify a full battery of 4, 8, 16, and 32-foot stops, but simply the combination of some _prestants_ and mixtures with a diapason or a bourdon.[3] As for a means of varying the intensity of the same tone, such a thing was never thought of. [Footnote 3: The French are accustomed to group registers of similar quality, but varying in pitch, under a single name; as _bourdons_ (stopped wood pipes), _montres_ (diapasons), _anches_ (reeds), qualifying them by the pitch; _e.g._, _bourdons_ of 16' and 8' would be equivalent to our bourdon and stopped diapason, or _gedackt_.--TR.] As I have said elsewhere, it is hardly farther back than to the end of the last century that we trace the invention of the "swell-box," the English contrivance which the aged Händel pronounced admirable, and which Abbé Vogler recommended to the German builders some years later. To-day, to non-professionals, our instruments appear to have become capable of nearly as much expression as the orchestra.