The basis of this method consisted in refinement of touch, for the attainment of which a natural, easy position of the hand was considered by Chopin a prime requisite. He prepared each hand with infinite care before permitting any attempt at the reproduction of musical ideas. In order to place it to advantage he caused it to be thrown lightly on the keyboard so that the five fingers rested on the notes E, F sharp, G sharp, A sharp and B, and without change of position required the practice of exercises calculated to insure independence. The pupil was instructed to go through these exercises first staccato, effected by a free movement of the wrist, an admirable means of counteracting heaviness and clumsiness, then legato-staccato, then accented legato, then pure legato, modifying the power from pp to ff, and the movement from andante to prestissimo. He was exceedingly particular about arpeggio work, and insisted upon the repetition of every note and passage until all harshness and roughness of tone were eliminated. "Is that a dog barking?" he was known to exclaim to an unlucky pupil whose attack in the opening arpeggio of a Clementi study lacked the desired quality. A very independent use of the thumb was prescribed by him. He never hesitated about placing it on a black key when convenient, and had it passed by muscle action alone in scales and broken chords whose zealous practice in different forms of touch, accent, rhythm and tone were demanded by him. Individualization of the fingers was one of his strong points, and he believed in assigning to each of them its appropriate part. "In a good mechanism," he said, "the aim is not to play everything with an equal sound, but to acquire beautiful quality of touch and perfect shading." Of prime importance in his eyes was a clear, elastic, singing tone, one whose exquisite delicacy could never be confounded with feebleness. Every dynamic nuance he exacted of fingers that fell with freedom and elasticity on the keys, and he knew how to augment the warmth and richness of tone-coloring by setting in vibration sympathetic harmonics of the principal notes through judicious employment of the damper pedal.