1. _The Great Preludes and Fugues_, with obbligato pedal. Their number cannot be stated, but I believe it not to exceed a dozen.(286) At least, after prolonged search I have not been able to collect more than that number.(287) To these I must add a very clever and original Passacaglia, which, however, seems suitable rather for a two-manual Clavicembalo and pedal than for the Organ.(288) 2. _Preludes on Choral Melodies_. It was at Arnstadt that Bach began to compose Variations on Choral melodies, under the title _Partite diverse._(289) Most of them can be played on the manuals alone. Those which I include here are an exception and require the obbligato pedal. Their number may amount to one hundred. I myself possess above seventy, and more survive elsewhere.(290) No other Choral Preludes approach them in religious feeling, dignity, and sublimity of expression. I cannot notice them individually; they are too numerous. Besides the larger, there is a great number of shorter and easier ones, particularly useful for young players. MSS. of them exist in considerable number.(291) 3. _Six Sonatas_, or Trios, for two manuals and an obbligato pedal.(292) Bach wrote them for his eldest son, Wilhelm Friedemann, whom they helped to become the great performer he was when I knew him. It is impossible to overpraise their beauty. Bach composed them when he was in the full vigour of his powers, and they may be considered his chef d’oeuvre in this form.(293) He also wrote other Organ Sonatas, the MSS. of which are in various collections. They are fine compositions, though they do not equal the Six in merit.(294) IV. Instrumental Music There are few instruments for which Bach did not write. In his day it was usual to play a Concerto or instrumental Solo during the Communion office.(295) Bach composed many of these pieces himself, and always with a view to their improving the technique of the player. Most of them are lost. But two important works of another kind survive and to some extent compensate us. They are: 1. Six Solos for Violin, unaccompanied.(296) 2. Six Solos for Violoncello, unaccompanied.(297) The Violin Solos have long been considered by the finest players to be the best instructor for the instrument. The Violoncello Solos are equally effective.(298) V. Vocal Music