=C. P. E. Bach’s Sonatas=.—His most enduring and important work was in connection with the pianoforte sonata, since under his hands it began to assume _definite shape_. In the six sets of sonatas published, the number of movements is generally fixed at three, of which the third is frequently in the harmonic form of the Rondo, which consists in the recurrence of a principal theme, with modulatory episodes between its appearances. Hence the order of movements, which, in the earlier writers, took all sorts of forms from fugue to dance form, becomes Allegro, Adagio, Rondo. Bach’s _themes_ are also made very characteristic, founded upon some easily-recognized _instrumental figure_. In the _development_ portion of the sonata form he does not resort to the polyphonic style, but _uses phrases or sections from the first part in new combinations and keys_. Sometimes, also, the direction is given in the repeat of the first section, to introduce variations of the text at will. =His Theoretical Works=.—Bach published at Berlin, in 1753, an essay on “The True Method of Playing the Clavier,” in which he gives a definite exposition of his father’s reforms in playing, treating the position of the hand, embellishments and artistic rendering, which he says should touch the hearts of the hearers. A second part, published in 1762, discusses the science of accompaniment and improvisation. =Adoption of the Piano=.—The clavichord, notwithstanding its feeble tone, remained his favorite instrument on account of its powers of expression, in which he delighted. His brother, Johann Christian, was one of the first definitely to adopt the new pianoforte. J. G. Müthel published in 1771 what were probably the first compositions mentioning the pianoforte for their performance, a duet for two pianofortes or harpsichords; after the time of C. P. E. Bach, clavier compositions were written in general distinctively for the pianoforte and not for the clavier. REFERENCES. Weitzmann.—History of Pianoforte Playing. Shedlock.—The Pianoforte Sonata. Grove.—Dictionary of Music and Musicians, article “Sonata.” Parry’s “Evolution of the Art of Music,” Chapter IX. Henderson.—How Music Developed, Chapter X. MUSICAL ILLUSTRATIONS. Weitzmann, pages 338, 340, 342-355. Rimbault.—“The Pianoforte,” pages 357-368. Edition Litollf, Augener, Breitkopf, as for Chapter IV. Works of C. P. E. Bach, in Peters’ edition. QUESTIONS AND SUGGESTIONS. What forms of composition were being worked out while the polyphonic style was reaching a culmination? What style had been most prominent in the early sonata? What points had been agreed upon as necessary in the construction of the sonata? What changes were made from the simple dance form? In what part of the sonata did the greatest change occur? What was the course of development in sonata form up to Haydn? Tell about Kuhnau and his work.