Haydn's first quartet is the merest shadow. The first half of the opening movement consists of no more than twenty-four bars. The subject comprises eight bars; then comes eight bars of an episode modulating into the dominant, and then the second subject, also eight bars in length; but brief and pale as it is, it is unmistakably the germ that was elaborated by Beethoven into such prodigious masterpieces. It is in the quartet that Haydn found the fullest outlet for his wealth of musical thought, and it is in the quartet that his genius is illustrated in its most marked individuality. Quartets were written before his day, and also by his contemporaries, J. C. Bach, Stamitz, Jomelli, Boccherini, and others, but Haydn's marvellous invention, his originality in the mastery of form, his fine feeling for the characteristic speech of each instrument enabled him to obtain a mastery that left him without a rival. His early quartets are exceedingly thin, and are in such glaring contrast with what came after the composer had wholly developed the capacity of the quartet as a means of profound expression of musical thought, that he is said to have wished to ignore all his works in this class that preceded the nineteenth quartet; but they are necessary to the student who would follow the growth of musical form. It is an immense stride from the first of these compositions to the ever-beautiful "Kaiser quartet," with its exquisite variations, or "Gott erhalte Franz den Kaiser." The advance from simple harmonies to polyphonic treatment of the different parts, is a peculiarly interesting subject for study. Haydn stamped a character on the quartet that has never been departed from; and what is known as the "quartet style" was established by him so thoroughly that in all the mutations in musical taste, it still remains a distinction that admits of no change. Haydn also left the impress of his genius on the sonata, though to Emanuel Bach is due the honor of having broken with the past as represented by Domenico Scarlatti and Kuhnau. The same copiousness of invention and perfection of form that characterize his quartets and symphonies are to be found in his sonatas, too much neglected at present, for in several of his later compositions of this class he appears to have gone further than Mozart and to have overlapped into the era of Beethoven. His trios for clavier and strings are full of interest, but with two or three exceptions they are not of special value except as models. The strings are often held subordinate to the piano, and the outer voices are too persistently doubled. Of his other purely instrumental works, including concertos and divertimenti, nothing survives except the fine concerto for clavier in D with "principal violin."