Emmanuel Bach is best known by six collections of sonatas and other compositions published at Leipsic between 1779 and 1787. In these sonatas the composer's resolute and final departure from the old polyphonic style is fully demonstrated. To enter wholly into the monophonic method of writing was no small undertaking, and we meet with many evidences of effort in these works. But the "working out" part of the sonata is always monophonic. The composer takes passages or phrases from his original melody, and treating them with changes of pitch, harmonic modulation, and bits of passage-writing, founded on figures previously used in the statement of the theme, he makes a musical exposition of his original idea. This is precisely what later composers did, but they had better command of the monophonic style, and hence produced better music than Emmanuel Bach. [Music: OPENING OF A MOVEMENT BY E. BACH, SHOWING CHANGE FROM POLYPHONIC STYLE.] The reader should now be in a position to understand that it is expected that at least one of the three or four contrasting movements of a sonata should be in what is called sonata form. This is almost always the first movement, in accordance with the general design of movements already given. This movement consists of three parts, which may be called proposition, discussion, and conclusion. The propositional part proposes a theme or themes; the discussion subjects the theme or themes to every device of musical treatment; and the conclusion restates the themes in their original form and brings the movement to a restful finish. Up to the point at which we have now arrived composers proposed, as a rule, only one theme for discussion. Occasionally a second was introduced, but it seems to have been merely episodal. We now come to the time when two themes were employed systematically, and from that time dates the establishment of the complete outline of the present sonata form. All the changes since made are in details. The composer by whom this important work was done was Haydn. Josef Haydn was born April 1, 1732, in Rohrau, Austria. He studied first at home and afterward at Vienna. In 1759 he became conductor of a small orchestra maintained by Count Morzin, and in 1760 he married a wigmaker's daughter, who had been his pupil. In 1761 Haydn became conductor of the orchestra of Prince Esterhazy at Eisenstadt, where he remained thirty years industriously composing. He became acquainted with Mozart, for whom he entertained the highest admiration. In 1790 he visited London and was received with great enthusiasm, so that he made a second visit in 1794. He died May 31, 1809, eighteen years before the death of Beethoven, and four years before the birth of Wagner. His music, therefore, brings us into close connection with the present period. His music is accessible to players of the piano, and there are good editions of his sonatas.