His system of tempering or tuning the clavichord, by reason of which he has often been granted a historical immortality, was the relatively simple one of dividing the octave into twelve equal intervals. Only the octave itself was strictly in tune, but the imperfections of the other intervals were so slight as to escape detection by the most practised ear. By paying the nominal toll of theoretical inaccuracy, Bach opened the roads of harmonic modulation on every hand. It must not be forgotten, however, that most of the pieces of Couperin or Scarlatti, not to mention many an outlandish chromatic tour de force in the works of the early English composers, would have been intolerable on a harpsichord strictly in tune. Other men than Bach had their systems of temperament. We may take Bach’s only to be the simplest.
Furthermore, that he created a new development of pianoforte technique by certain innovations in the manner of fingering passages, is open to question. It is well known that up to the beginning of the eighteenth century the use of the thumb on the keyboard was generally discountenanced. Bach himself had seen organists play who avoided using the thumb even in playing wide stretches. Scales were regularly played by the fingers, which, without the complement of the thumb, passed sideways over each other in a crawling motion which is said to have been inherited from the lutenists. Couperin advocated the use of the thumb in scales, but over, and not under, the fingers. Bach seems the first to have openly advised and practised passing the thumb under the fingers in the manner of today. Yet even he did not give up entirely the older method of gliding the fingers over each other in passages up and down the keyboard.
His system passed on through the facile hands of his son Emanuel, the greatest teacher of the next generation; and if it is not the crest of the wave of new styles of playing which was to break over Europe and flood a new and special pianoforte literature, is at any rate a considerable part of its force. Yet it must be borne in mind that Scarlatti founded by his own peculiar gifts a tradition of playing the piano and composing for it, in which Clementi was to grow up; and that, influential as Emanuel Bach was, Clementi was the teacher of the great virtuosi who paved the way to Chopin, the composer for the piano par excellence.
The foundation of all Bach’s music is the organ. Even in his works for violin alone, or in those for double chorus and instruments, the conjunct, contrapuntal style of organ music is unmistakable. His general technique was acquired by study of the organ works of his great predecessors, Frescobaldi, Sweelinck, Pachelbel, Buxtehude, Bohm, and others. He was first and always an organist. So it is not surprising to find by far the greater part of his harpsichord and clavichord music shaped to a polyphonic ideal; and, what is more, written in the close, smooth style which is primarily fitting to the organ.
His intelligence, however, was no less alert than it was acute. There is evidence in abundance that he not only knew well the work of most of his contemporaries, but that he appropriated what he found best in their style. He seems to have found the violin concertos of Vivaldi particularly worthy of study. He was indebted to him for the form of his own concertos; and, furthermore, he adapted certain features of Vivaldi’s technique of writing for the violin to the harpsichord. Of the influence of Couperin there is far less than was once supposed. The ‘French Suites’ were not so named by Bach and are, moreover, far more in his own contrapuntal style than in the tender style of Couperin. Kuhnau’s Bible sonatas are always cited as the model for Bach’s little Capriccio on the departure of his brother; but elsewhere it is hard to find evidence of indebtedness to Kuhnau.
But he even profited by an acquaintance with the trivial though enormously successful Italian opera of his day, and used the da capo aria as frankly as A. Scarlatti or J. A. Hasse. Still, whatever he acquired from his contemporaries was but imposed upon the great groundwork of his art, his organ technique. He never let himself go upon the stream of music of his day, but held steadfast to the ideal he had inherited from a century of great German organists, of whom he was to be the last and the greatest.
So, for the most part, the forms which had evolved during the seventeenth century were the forms in which he chose to express himself. Of these, two will be for ever associated with him, because he so expanded them and filled them with his poetry and emotion that no further growth was possible to them. These are the fugue and the suite.
V
Most of Bach’s predecessors and many of his contemporaries regarded the fugue as the highest form of instrumental music. It was the form in which they put their most serious endeavor. The harmonic basis of music was generally accepted and skill in weaving a contrapuntal or a polyphonic piece out of a principal motive or theme, and two or three subsidiary ones, was more or less common to all musicians. Yet fugues up to the time of Bach lacked a logical unity of construction. Excellent as the craftsmanship displayed in them might be, the effect was not satisfactory. There seemed, for instance, to be no very clear reason why a fugue should end except that the composer chose to end it. There was no principle of balance governing the work as a whole. It was architecturally out of proportion, or it failed to impress its proportions upon the listener. Bach alone seems to have given the fugue a perfectly balanced form, to have endowed it not only with life but with organization as well.
The secret of this is that at the bottom of his fugues lies a broadly conceived, well-balanced and firmly constructed harmonic plan. It must be granted, besides, that the subjects out of which he builds them have a singular vitality and are full of suggestion. But Bach, with his fertility in highly charged musical ideas and his apparently unlimited power to weave and ravel and weave musical material in endless variety of effects, rarely let his skill or his enthusiasm betray his sense of proportion. There is a compactness in nearly all his fugues which results from the compression of expressive ideas within the well-defined limits of a logical, harmonic plan.