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.