Mozart did not compose his piano music at the piano, as Schumann and Chopin did. The improvisations were not remembered later and put down in form upon paper. They seem to have been something apart from his composing. He wrote music away from the piano, at his desk, as most people write letters--in the words of his wife. Most of the sonatas, too, were written for the benefit of pupils. Few of them make actually trying demands upon technical brilliance. Their great difficulty is more than technical, or than what is commonly regarded as technical--strength, velocity, and endurance. Yet no music more instantly lays bare any lack of evenness or any stiffness in the fingers. Mozart cared little for a brilliant style. His opinion of Clementi has already been mentioned. He preferred rather a moderate than an extremely rapid tempo, condemned severely any inaccuracy or carelessness, likewise any lack of clearness in rhythm. But, above all, he laid emphasis on a beautiful and singing quality of tone. His avoidance rather than cultivation of brilliancy alone makes his music often suggest the harpsichord. There is an absence of the technical devices then new, which have since become thoroughly associated with the pianoforte style. Yet from 1777 Mozart devoted himself to the pianoforte. An instrument made especially for him, which he invariably used in his many concerts in Vienna, has been preserved. The keyboard has a range of five octaves, from the F below the bass staff to the F above the treble staff. The action is very light, the tone rather sharp and strong. It can be damped, or softened, by means of a stop which pulls a strip of felt into position between the strings and the hammers. Concerning the pianoforte sonatas it may be said again that few depart from a normal, prevailing mood. Some are exceptional. Knowing his great gift of improvising and how rich and varied his improvisations were, it is perhaps a temptation to read into them more definite emotions than are really implied. Yet it is easy to pick from the later sonatas at least three which not only differ considerably from the earlier sonatas, but differ likewise from each other. Nevertheless, two or three traits are common to them all. They mark Mozart’s sonatas distinctly from Haydn’s and, indeed, from all other sonatas.