The Concertos are written on various scales, the use of one instrument concertante being extended to Concerti Grossi requiring as many as four. For the harpsichord there exists six; for two harpsichords two, and for three again two. In another concerto he has combined the harpsichord with two flutes, and in two more with flute and violin, as the three obbligato instruments.
For the violin Bach composed three concertos, besides one apiece for two violins, for violin and hautboy, for two flutes and violin, and for flute, violin, hautboy, and trumpet.
Orchestral works, but for an orchestra of very various constitution, are three of the so-called Brandenburg Concertos,[31] and four parties or suites which rank among the most flexible and melodious of all Bach’s creations.[32] The list would be increased by nearly thirty works if we added the instrumental symphonies which occur in the course of his cantatas.
As strict chamber music we may reckon his three sonatas or trios, in which the harpsichord combines respectively with two flutes, flute and violin,[33] and two violins. For harpsichord and flute there are six sonatas; for harpsichord and violin a like number, together with three separate pieces, a sonata, a partie, and a fugue; finally, three sonatas for harpsichord and viola-da-gamba.
The list of Bach’s instrumental works is completed by two sonatas for obsolete instruments, one for the lute, the other for his own invention, the viola pomposa, and by the memorable sets, of six sonatas each, for the violin and violoncello, which are well enough known in England to render an account of them superfluous.
But a few words are needed in conclusion to mark Bach’s position in reference to the clavichord. In the first place, being acutely sensible of the least falsity of tune, he always tuned the instrument himself, a process which never cost him more than a quarter of an hour. In this art he introduced a great reform, that of tuning on a basis of equal temperament. Without such a reform his chromatic music, and notably his Chromatic Fantasia and the Wohltemperirte Clavier, would have been impossible. Another instance of his fastidious taste is that no one but himself could adjust the quills of a harpsichord to his satisfaction. He took great pains in improving the action of the clavichord, and invented a new instrument, the lute-harpsichord (lauticlavicymbel), with a surprising brilliancy of tone; but the difficulty of tuning it led to its abandonment.
It would demand too technical a discussion if we were to analyse the method of playing which Bach introduced. That he was the first to insist upon an equal use of the thumb with the rest of the hand, and to act upon the principle that touch proceeds from the lower joints of the fingers, and not from the wrist or arm, makes him the founder of the modern art of piano-playing. It is said of him that he “played with so easy and small a motion of the fingers that it was hardly perceptible. Only the first joints of the fingers were in motion; the hand retained, even in the most difficult passages, its rounded form; the fingers rose very little from the keys, hardly more than in a shake, and when one was employed, the others remained still in their position. Still less did the other parts of his body take any share in his play, as happens with many whose hand is not light enough.”[34] His playing was light, smooth, swift—powerful or expressive, as he chose—but always without display or the appearance of effort.