The method of composition employed by the early masters of orchestral music was elaborate, yet not recondite. It was a system of architecture in tones, and its achievements were distinctly satisfying to the æsthetic discernment and to the appetite of the human mind for a logical arrangement of ideas. Four parts or movements were allotted to a symphonic work. Contrast of time, rhythm, key, and harmonic color was sought. Each movement differed from that next to it. Variety in unity was the ultimate object. But each movement had to have a well-defined shape within itself. Two melodic ideas, complementary to each other in key, rhythmic nature, and sentiment, were invented. They were held up for the inspection of the hearer at the beginning of the movement Then the composer embarked upon what was called the "working out." He took the essential features of his two melodies and juggled them through the tricks of musical metamorphosis. He dressed them in new harmonies; he made them writhe in the embraces of counterpoint; he expanded them into new melodies; he sang them with the different voices of the instrumental body. In the end he repeated them in their original shape, and brought his movement to a close. The entire purpose was the treatment of themes. The only aim was to make symmetrical, intelligible, interesting music. In evolving this form the composers fell, as I have said, into a conventional use of their orchestra. They had three choirs, one of wooden wind instruments, one of brass, and one of strings played with bows. They allotted fixed functions to each choir and to the members of each, and there they stopped. Occasionally a hint from the operatic treatment of the instruments enlightened them and they made a slight advance, but nevertheless, when Beethoven came to write his symphonies, in which he attempted to make orchestral music attain something more than mere musical beauty, he found himself hampered by the conventionalities of symphonic orchestration, as well as by those of the symphonic form. It was the limitation of the form, indeed, which restrained the instrumentation. The form itself had first reached definiteness with Haydn, who died when Beethoven was thirty-nine. Only in his later years did Haydn learn the use of clarinets, the most important members of the wood wind choir.