Whether his sonatas of the Vienna period are solo or accompanied by other instruments, they have only three movements. He first sought beauty of melody, for song was to him the foundation, the highest expression of music. Therefore the themes were carefully sung, and the second subject was made of more importance by him than by his predecessors. Often the chief effect in his sonata movements as in his concertos is gained by the delivery of a sustained melody, and these melodies written for his own hands show the influence of the peculiar characteristics of his own performance. Frequently in the elaboration of the themes he introduced new melodies, so that we find Dittersdorf complaining of the prodigality of the composer, who "gives his hearers no time to breathe." When he used polyphony, it was not to display pedantry but to accentuate the beauty of the themes. The slow middle movements are in song form, and are full of emotion and tender grace; eminently spontaneous, and coming from the heart. The final movements are generally the weakest. They show the facility with which he wrote, and their gayness often approaches triviality. Passing over the pianoforte compositions for two performers and for two pianofortes--not that they are unworthy of attention-- we come to the sonatas with violin accompaniment, which, during the Vienna period, were, many of them, written for pupils. They are characterized by beautiful melodies and bold harmonies rather than by any great depth or exhibition of scholarship. The violin part is independent, and not an accompaniment, as was usual at the time. The trios or terzets for pianoforte, violin and 'cello were chiefly written for amateurs to play in musical parties. Violoncellists of any force were rare in these circles, and it is not unlikely that this was a serious hindrance to Mozart's further development of the trio. Far greater in breadth of design and in thematic elaboration are the two pianoforte quartets (1785 and 1786). The trios were written for social purposes, and brilliancy was perhaps too much cultivated; but in these quartets passion enters, strong and fierce and bitter. In 1784 Mozart wrote his father that his quintet in E-flat major for pianoforte, oboe, clarinet, horn, and bassoon, which was received with great applause in a concert given by him in the theatre, was the best thing he had ever written, and he chose it to play before Paesiello. It is certainly a composition of remarkable beauty, not so much on account of its thematic invention as for its intimate knowledge of the peculiarities of the different instruments and for the balance of euphony preserved throughout. The pianoforte concertos, of which seventeen were written in Vienna, were, as a rule, intended for his own concert use. He described the first three as "a happy medium between too easy and too difficult." He added in this letter to his father, that "even ignoramuses will be pleased with them without