His son and pupil, Philipp Emanuel Bach (1714-1788), proceeding on the principles established by his illustrious father, prepared the way for the modern pianist.  His important theoretical work, “The True Art of Clavier Playing,” was pronounced by Haydn the school of schools for all time.  It was highly extolled by Mozart, and to it Clementi ascribed his knowledge and skill.  In his compositions he was an active agent in the crystallization of the sonata form.  From him Haydn gained much that he later transferred to the orchestra.

Impulse to the second period of clavier virtuosity was given by Wolfgang Amadeus Mozart (1756-1791) and Muzio Clementi (1752-1832).  Mozart, who led the Viennese school, developed the singing style of playing and the smooth flowing legato.  Leaving behind him the triumphs of his wonder-boyhood with spinet and harpsichord, he boldly entered the public concert-hall with the pianoforte, now greatly advanced by the improvements of Silbermann.  Mozart brought into use its special features, showed its capacity for tone-shading and for the reflection of sentiment, and may well be said to have launched it on its career.  Tradition declares that his hand was fashioned for clavier keys, and that its graceful movements afforded the eye no less pleasure than the ear.  His noble technique, based on his profound study of the Bachs, was spiritualized by his own glowing fancy.  In his playing, as in his compositions, every note was a pearl of great price.  With his piano concertos he showed how clavier and orchestra may converse earnestly together without either having its individuality marred.  The same equilibrium is maintained in his piano and violin sonatas and his other concerted chamber music, amid all their persuasive and eloquent discourse.  His charming four-hand and double piano pieces, written for himself and his gifted sister Marianne, and his solo clavier sonatas would prove his wealth of musical invention had he not written another note.

Clementi, born in Rome, passed most of his life in London, where he attracted many pupils.  Without great creative genius, he occupied himself chiefly with the technical problems of the pianoforte.  He opened the way for the sonority of tone and imposing diction of the modern style.  His music abounded in bold, brilliant passages of single and double notes.  He is even credited with having trilled in octaves with one hand.  Taking upon himself the management of an English piano factory, he extended the keyboard, in 1793, to five and a half octaves.  Seven octaves were not reached until 1851.  His “Gradus ad Parnassum” became the parent of Etude literature.  Carl Tausig said:  “There is but one god in technique, Bach, and Clementi is his prophet.”

Losing the spirituality of a Mozart the Viennese school was destined to degenerate into empty bravura playing.  Before its downfall it produced a Hummel, a Moscheles and a Czerny, each of whom left in their piano studies a valuable bequest to technique.  Karl Czerny (1791-1857), called king of piano teachers, numbered among his pupils, Liszt, Doehler, Thalberg and Jaell.  The Clementi school was continued in that familiar writer of Etudes, Johann Baptist Cramer (1771-1858), and began to show respect for the damper pedal.  Its most eminent virtuoso was John Field (1782-1837) of Dublin.