The ‘Viennese period’ and the three great classics--Joseph Haydn; Haydn’s clavier sonatas; the Variations in F minor--W. A. Mozart; Mozart as pianist and improvisator; Mozart’s sonatas; his piano concertos--Ludwig van Beethoven; evolution of the modern pianoforte--Musical qualities of Beethoven’s piano music; Beethoven’s technical demands; his pianoforte sonatas; his piano concertos; conclusion. The association of Haydn, Mozart, and Beethoven with Vienna affords historians a welcome license to give to a conspicuous epoch in the development of music a local habitation and a name. Their work is commonly granted to constitute a more or less definite era known as the Viennese period. All three speak, as it were, a common idiom. There is a distinct family likeness between their separate accomplishments. They were personally acquainted. Haydn and Mozart were warm friends, despite the difference in years between them. Mozart was among the first in Vienna to recognize the greatness latent in Beethoven, who later was for a while even the pupil of Haydn. Moreover, all three reckoned among their friends the same families, even the same men and women. The three great men now sit on golden chairs, enshrined in the same niche, Beethoven considerably to the fore. The insulation which circumstances of time and space may seem to have woven about them proves upon investigation to be quite imperfect. To begin with, Bach was but a year dead, D. Scarlatti still alive, and Rameau with more than a decade yet to live when Haydn was writing his first mass and along with it clavier sonatas for the benefit of his few pupils. Mozart had written his three immortal symphonies in 1786, before Emanuel Bach had ceased publishing his sonatas for _Kenner und Liebhaber_. On the other end, Moscheles was a famous though very young pianist before Beethoven had half done writing sonatas; and Carl von Weber’s _Freischütz_ had begun to act upon the precocious Richard Wagner before Beethoven had completed his ninth symphony, his last sonata, his great mass and his great quartets. Merely as regards pianoforte technique the period was a transitional one. Even the Beethoven sonatas as late as opus 27 were published for either harpsichord or pianoforte. Both Mozart and Beethoven were influenced by men who, in a narrow sense, seem far more than they to belong to a modern development. Clementi, for example, deliberately burned his harpsichords and clavichords behind him in the very year Beethoven was born, and from then on gave up his life to the discovery of new possibilities and effects upon the pianoforte, by which his pupils Cramer and Field paved the way for Chopin.