1. _Six Sonatas for Clavier with Violin obbligato_. Composed at Cöthen, they are among Bach’s masterpieces in this form and display fugal and canonic writing which is both natural and full of character. The Violin part needs a master to play it; for Bach knew the capabilities of the instrument and spared it as little as the Clavier. The six Sonatas are in the keys of B minor, A major, E major, C minor, F minor, and G major.(274) 2. _Several Sonatas for Harpsichord and Violin_,(275) _Harpsichord and Flute_,(276) _Harpsichord and Viol da Gamba_.(277) They are admirably written and most of them are pleasant to listen to even today.(278) 3. _Several Concertos for the Clavier and other instruments_. They contain real gems of art but are antiquated in form.(279) 4. _Two Concertos for two Claviers_, with an accompaniment of two Violins, Viola, and Violoncello. The first, in C minor,(280) has an antique flavour. But the second, in C major,(281) is as fresh as if it had been written yesterday.(282) It may be played without the String quartet and still sounds admirable. The final Allegro is a majestic movement and strictly fugal. Compositions of this form were first perfected, indeed, we may conjecture, were first attempted, by Bach. At least, I have met with only a single example by another composer that may perhaps be older—namely, Pachelbel of Nürnberg’s Toccata, as he called it. Pachelbel, however, was a contemporary of Bach and may have taken the idea from him. However, his work is not worth considering. One instrument merely repeats the other’s phrases without being at all concertante. It almost seems as if Bach at this period had made up his mind to discover what could be done with any number of parts. Having already written for a single solo instrument music which required no accompaniment, he next experimented in dividing his material between as large a number of solo instruments as possible. Hence the Concertos for two Claviers were followed by 5. _Two Concertos for three Claviers_ with an accompaniment of Strings.(283) These Concertos present a remarkable characteristic: besides the concertante combination of three Claviers, the stringed instruments also have concertante parts distinct from the accompaniment. It is difficult to realise the art involved in this achievement. For, in spite of their technical skill, the two works are so delicate, full of character, and expressive, that the composer might be treating a simple melody (note particularly the Concerto in D minor). Words are inadequate to express the admiration they arouse. But Bach was not satisfied. Hence he wrote 6. _A Concerto for four Claviers_ and four stringed