First of all, Mattheson, in his treatise upon thorough-bass,[113] furnishes the ground for our premise; he cites the following fugue subject as having been given to a candidate who was undergoing an examination for an organ position: [Music] with this countersubject: [Music] [Footnote 113: _Grosse General-Bass-Schule, oder Exemplarische Organistenprobe_ (Hamburg, 1731), p. 34. "The subject of this fugue was produced by a facile pen, and, in 1725, presented to a candidate for the position of organist."] He adds that this theme was well known, and that it had been chosen to assist the candidate in his task, since he would already have had an opportunity of hearing it treated; he says, further, that its origin was not unknown, and that it was well known who had been the first to make use of it with success. Mattheson, who wrote this about 1725, seems to be speaking of a theme unusually familiar. Was it not from Bach himself--the examination took place at Hamburg--that the candidate, who was from that city or a neighboring locality, would probably have heard a fugue composed upon this same subject? Moreover, an examination of the prelude will confirm this opinion. Through his study of the works of Buxtehude and of Reinken, the venerable organist, Bach had possessed himself of all their secrets. The opportunity had come for him to demonstrate to the organists of Hamburg how, in imitating them, he could surpass them on their own ground. For the characteristics of the prelude resemble those of the works of these men; recitatives, rapid passages which cover the entire compass of the manuals; chord progressions with bold, unforeseen modulations; subjects treated in imitation. But the recitatives are of an expressive, declamatory character which was then unheard of; the rapid passages are the forerunners of "those scales, those tremendous ascending and descending scales which rise and fall like the waves of the sea in a storm,"[114] which Mozart wrote in the overture to _Don Giovanni_; the chord progressions, with a daring which had never been exceeded, leading to that gigantic passage (measures 31 to 40), a veritable orchestral crescendo, where all resources of sonority deploy themselves in radiation, taking on new force with each strong beat; it serves also as an example of the crescendo which may be obtained upon the organ without recourse to modern appliances. Finally, the motive treated in imitation (measures 9 to 13) vouchsafes us a period of repose, corresponding to a point of temporary rest in the midst of chaotic agitation; it is the calm supplication of prayer which alternates with the power of the elements freed from their fetters. [Footnote 114: Charles Gounod: _Le Don Juan de Mozart_, p. 5.]