Bach’s organ works divide themselves into three great branches, the first of which is connected most closely with his religious office. It is well known that the German chorale since the days of Luther has always held its regular place in the service of the church. This form of melody, however much more beautiful, is essentially the same with what we in England used to sing as psalm tunes, at a time when one metrical version of the Psalter was employed and the modern hymn with its new words and heterogeneous structure had not yet made its voice heard. In Germany words and music were alike familiar to every one; they formed in fact the nucleus of Lutheran worship both in church and at home. We shall see hereafter how Bach collected two hundred and forty chorales for use in his household; and there are hardly any of his church cantatas which do not contain at least one. In church, whenever a chorale was announced, every one present could be trusted to sustain the melody, and it was allowed to the organist to vary the harmonies almost to any extent he pleased without fear of confusing the people.[17] In this way it came to be a recognised part of the organist’s function, at least in Middle Germany, to adorn the simple grandeur or pathos of the chorale by means of preludes, interludes, and variations, generally improvised at the moment; and this treatment of chorales was so popular, through the influence of Johann Christoph and Michael Bach, Pachelbel, and a number of leading organists just before Sebastian Bach’s time, that it became extended so as to form the basis of independent instrumental compositions, for use at other intervals in the church service. It was a custom of which Bach was peculiarly fond, giving him, as it did, a firm groundwork, with high associations, upon which his fancy could build with the utmost freedom. And though he wrote down but a minute part of what he composed, we possess in print no less than a hundred and thirty elaborations of chorales (parts 5-7), besides twenty-eight of which the genuineness is disputed (suppl. 9-36). They range from short and slight preludes to works of the most intricate brilliancy, abounding in all the science as well as in all the melodious art of which Bach was master. Those to whom the organ chorales are inaccessible may learn their spirit by unravelling the harmonies he has used in the fivefold setting of one chorale in the S. Matthew Passion or from other no less remarkable instances in that according to S. John, to quote only from works which are best known in England. The inexhaustible invention which is pressed into the brief compass of these verses, is in the organ-chorales distributed over a long composition; but the extension is never for the purpose of display, and the fundamental motive insistently maintains itself throughout.
In opposition to these the second branch of Bach’s organ works stands remote from the church. It was not choice only but also the determined bent of musical taste at Weimar that directed his study again to the instrumental music of Italy; and the influence for the present lay strongly upon his organ music as well as upon the rest of his compositions. Three of Vivaldi’s violin-concertos with a movement of a fourth (part 8, 1-4) he arranged for his instrument; he wrote fugues on themes by Legrenzi and Corelli[18] (4. 6, 8), and a fugue and canzone (8. 6; 4. 10) recalling the manner of the great Roman organist, Frescobaldi, whose Fiori Musicali, published in 1635, he possessed.
But it would be a great mistake to imagine that Bach was at this time engrossed by the Italian masters. On the contrary Weimar was the place where he wrote the bulk of his organ works of the third branch, the preludes, fantasias, toccatas, and fugues, in which his strong religious sense united with his power of musical creation to build up masterpieces of a perfection never approached either before or since. The list of his works of this period is as follows:—
1. Three Preludes, in A minor, C, and G (4. 13; 8. 8, 11):
2. Three Fugues, in G minor, C, and G minor (4. 7; 8. 10, 12):
3. Fifteen Preludes and Fugues in A, F minor, C minor, G minor, E minor, C, G, and D; besides a collection of eight shorter ones (2. 3, 5, 6; 3. 5, 10; 4. 2, 3; 8. 5. i-viii.):
4. Three Toccatas and Fugues, in F, C, and D minor (3. 2, 8; 4. 4):
5. Two Fantasias and Fugues both in C minor (3. 6; 4. 12): to which must be added three single works, namely a Fantasia in C (8. 9); a Pastorale in F (1. 3); and the superb Passacaglio in C minor, well known to all organists worthy of the name (1. 2).
For the years succeeding those he spent at Weimar, Bach has left us, with one grand exception, no certain record on the organ; we shall see hereafter that he was otherwise occupied. But there is hardly a doubt that he took advantage of the exceptional opportunity offered by his Hamburg visit in 1720, to produce his famous Fantasia and Fugue in G minor (2. 4). It does not surprise us to find that the Fugue, which English musicians have personified as the Giant, left an abiding impression among the listeners.[19] As we possess it, it has undergone a rigorous revision, to which, in common with the major part of his younger works, Bach afterwards submitted it when at Leipzig.
Accordingly the short series which he is believed to have composed in later years does not represent more than a fraction of his activity in this direction; since revising in his case usually meant re-writing, certainly re-thinking. The compositions which are presumed to date originally from the year 1723 onwards, consist of seven Preludes and Fugues, in C, G, A minor, E minor, B minor, E flat, and D minor,[20] (2. 1, 2, 8, 9, 10; 3. 1, 4), and a Toccata and Fugue in D minor, known as the Doric toccata (3. 3); together with six Sonatas written to exercise the growing skill of Bach’s eldest boy, Wilhelm Friedemann (1. 1).[21]