The string quartet had its birth almost simultaneously with the symphony, and is also the child of Haydn’s genius. Its ancestors are considered by Jahn to be the divertimenti and cassations designed for table music, serenades, and such entertainments, and written often in four or five movements for four wind instruments, wind instruments with strings, or even for clavier. This species of composition was transferred, curiously enough, to two violins, viola and bass--the latter being in time replaced by the 'cello. This combination of instruments, so easily available for private use, appealed especially to Haydn, and his later compositions for it are still recognized as models. The quartet, like the symphony, is based on the sonata form, and developed gradually, in a manner similar to the larger work. Haydn’s first attempt in this species was made at the age of twenty-three, and eighty-three quartets are numbered among his catalogued works. The early ones are very like the work of Boccherini, and consist of five short movements, with two minuets. As Haydn progressed his tendency was to make the movements fewer and longer. After Quartet No. 44 the four-movement form is generally used, and his craftsmanship grows more delicate. Gradually he filled the rather stiff and formal outline with ideas that are graceful and charming, even though they may sound somewhat elementary to modern ears. He recognized the fact that in the quartet each individual part must not be treated as solo, nor yet should the others be made to supply a mere accompaniment to the remainder. Each must have its rôle, according to the capacity of the instrument and the balance of parts. The best of Haydn’s quartets exhibit not only a well-established form and a fine perception of the relation of the instruments, but also the more spiritual qualities--tenderness, playfulness, pathos. He is not often romantic, neither is there any trace of far-fetched mannerisms or fads. He gave the form a life and freshness which at once secured its popularity, even though the more scientific musicians of his day were inclined to regard it with suspicion, as a trifling innovation. Nevertheless, it was the form which, together with the symphony, was to attest the greatness of Mozart and Beethoven; and it was from Haydn that Mozart, at least, learned its use.