C. P. E. Bach was only concerned with the first volume. Erk, in his edition of the Choralgesänge, conjectures that Kirnberger was responsible for the second.
The four volumes were published at Leipzig between 1784-87. Spitta states that C. P. E. Bach was the editor. Erk joins Kirnberger with him in that position. As C. P. E. Bach died in 1788 Kirnberger's association with the work is probable, especially if he had already been responsible for the 1769 volume.
Bach's Clavier school consisted of eighteen Preludes for beginners (all in B.G. XXXVI.); the two-part and three-part Inventions; and the Well-tempered Clavier. The six Preludes mentioned by Forkel, and which alone he knew, were published by him for the first time. Seven more are found in Wilhelm Friedemann's Clavierbüchlein (B.G. XLV. (1)), and the remaining five have survived in texts handed down by others of Bach's pupils. The eighteen are in P. bk. 200.
The Autograph was written at Cöthen and is dated 1723. It also contains the fifteen Symphonies, or three-part Inventions mentioned in paragraph 3. Both Inventions and Symphonies are in F. bk. 201. According to Spitta (ii. 57 n.) the Inventions were published at Leipzig in 1763. See also Schweitzer, i. 328 ff.
See the previous note.
The second Part was compiled in 1744 and Bach's Autograph of it, though not the earliest Autograph, is in the British Museum. See Schweitzer, i. 331 ff. and Spitta, ii. 161 ff. The whole work is in P. bks. 1, 2; or 1a, 1b; or 2790a, 2790b.
No. 20. Spitta (ii. 164) attributes it to the years 1707 or 1708. Schweitzer (i. 332) also regards it as a youthful piece written, moreover, for the pedal Clavicembalo.
Nos. 15 and 16. Spitta, admitting that the two do not rank with the most interesting in the collection, finds no indication of their being of different date from the best movements.
No. 1. Here Spitta (ii. 165 n.) challenges Forkel.
Nos. 11 and 12. In regard to No. 12 (F minor) Spitta holds Forkel to be in error. As to No. 11, he expresses the same opinion as in note 3, supra.