it—it is not equally indispensable with Couperin, whose thematic material was not so intricate as Bach’s, nor did he compose or play in such difficult keys. Consequently Couperin had not an equally urgent need to use the thumb. We need only compare Couperin’s with Bach’s system of fingering, as Carl Philipp Emmanuel explains it,(124) to discover that Bach’s permits every passage, however intricate and polyphonic, to be played with ease, whereas Couperin’s is hardly effective even for his own compositions. Bach was acquainted with Couperin’s works and highly esteemed them,(125) as he did those of other French Clavier composers, for their finish and brilliance. But he considered them affected in their excessive use of ornaments, scarcely a single note being free from them. He held them, also, superficial in matter. Bach’s easy, unconstrained use of the fingers, his musical touch, the clearness and precision of every note he struck, the resourcefulness of his fingering, his thorough training of every finger of both hands, the luxuriance of his thematic material and his original method of stating it, all contributed to give him almost unlimited power over his instrument, so easily did he surmount the difficulties of its keyboard. Whether he improvised or played his compositions from notes, he systematically employed every finger of each hand, and his fingering was as uncommon as the compositions themselves, yet so accurate that he never missed a note. Moreover, he read at sight other people’s compositions (which, to be sure, were much easier than his own) with the utmost facility. Indeed, he once boasted to a friend at Weimar that he could play at sight and without a mistake anything put before him. But he was mistaken, as his friend convinced him before the week was out. Having invited Bach to breakfast one morning, he placed on the Clavier, among other music, a piece which, at a first glance, seemed perfectly easy. On his arrival, Bach, as was his custom, sat down at the Clavier to play or look through the music. Meanwhile his friend was in the next room preparing breakfast. In a short time Bach took up the piece of music destined to change his opinion and began to play it. He had not proceeded far before he came to a passage at which he stopped. After a look at it he began again, only to stop at the same place. “No,” he called out to his friend, who was laughing heartily in the next room, “the man does not exist who can play everything at sight. It can’t be done.” With that he got up from the Clavier in some annoyance.(126)