This treatment of the character of the movements grew out of the crude attempts of the earliest writers and was formulated in the concertos of Sebastian Bach, but more clearly in the piano sonatas of his son Carl Philip Emmanuel Bach. Previous to that, however, something had been done toward a definite arrangement of the distribution of keys. To this Domenico Scarlatti, who has already been mentioned, made some important contributions. His compositions called sonatas have a distinct melodic subject, and this is preserved throughout. His first movements foreshadow the shape which the first movements of the classical sonatas subsequently assumed. These movements are divided plainly into two parts, and each part is repeated. Each of them opens with an announcement of the melodic subject in the tonic key of the sonata. After stating his subject Scarlatti passes into a key closely related to that of the sonata, and gives a bit of what is called "passage work;" that is, florid or ornamental piano writing without a complete tune. The second part embarks upon a brief musical development of the subject by means of simple musical changes in its original shape, then modulates back into the original key, restates the beginning of the movement and comes to an end. One of the peculiarities of his works is that sometimes in the musical development ("working out," as it is called) of his theme he introduces a new melody, different from the first. Later writers caught at this idea and raised this second melody to an importance equal to that of the first. Scarlatti's great contemporary, Johann Sebastian Bach, did not stand in the direct line of development of the piano sonata. As I have tried to show in writing of clavichord works, his sympathies when composing for a keyboard instrument were governed largely by his immense genius for the organ and his profound insight into the nature and scope of polyphonic composition. Nevertheless, his violin sonatas, the result of a close and admiring study of those of Corelli and Vivaldi, show a leaning toward the modern form. He followed the lines laid down by Corelli. All but one of his violin sonatas are in four movements, the first and third slow, and the second and fourth lively. The slow movements, as one would naturally expect from Bach, are intense in their emotional eloquence. But Bach's manner of development was almost always polyphonic, and this was hostile to the sonata method, which was radically monophonic.