"A musical performer will play a piece which has become familiar by repetition while carrying on an animated conversation or while continuously engrossed by some train of deeply interesting thought; the accustomed sequence of movements being directly prompted by the sight of the notes, or by the remembered succession of the sounds (if the piece is played from memory), aided in both cases by the guiding sensations derived from the muscles themselves. But, further, a higher degree of the same 'training' (acting on an organism specially fitted to profit by it) enables an accomplished pianist to play a difficult piece of music at sight; the movements of the hands and fingers following so immediately upon the sight of the notes that it seems impossible to believe that any but the very shortest and most direct track can be the channel of the nervous communication through which they are called forth.
