The last of these quartets, in C major (K. 465), is the most profound and the most impassioned. The boldness of Mozart’s imagination in harmonies is in most of his work likely to fail to impress the modern ear. One hears but half-consciously the subtlety of his modulations. But here and there in his work the daring of the innovator still has power to claim our attention; as in the andante of the last pianoforte sonata in F major (K. 533), and still more in the introduction of this quartet. The sharp harmonies of the first few measures roused hostility; and the discussion as to their grammatical propriety was continued for more than half a century after Mozart’s death.
The whole quartet is full of an intensity of feeling. The andante has that quality of heart-melting tenderness which sprang only from Mozart’s genius. One cannot but place the four movements with the three great symphonies, as something not only immortal, but precious and inimitable in the world’s treasure of instrumental music.
This series of six quartets did not make a decidedly favorable impression upon the general public. The next quartet from his pen was in a much more conventional manner, as if Mozart had tried to suppress the genius in him which prompted him ever to new discoveries in his art. The quartet in D major (K. 499) was composed on the 19th of August, 1786. It is beautifully worked in detail, light in character. No special reason is known why he should have written and published a single quartet like this; and it has been thought that he hoped by it to rouse the public to enthusiasm for his instrumental works.
There remain three more quartets to mention. These were written for Frederick William II of Prussia, at whose court Mozart had been a frequent attendant during the early spring of 1789. The first quartet was completed in Vienna, in June, 1789. The other two were written about a year later. In Köchel’s index the three are Nos. 575, in D major, 589, in B-flat major, and 590, in F major.
All are very plainly written with a king in mind who played the violoncello. In most of the movements the 'cello is given a very prominent part, frequently playing in unusually high registers as in the announcement of the second theme in the first movement of the first of these quartets; in the trio and the finale as well. In many places the viola plays the bass part, leaving the 'cellist free to be soloist, as in the opening measures of the Larghetto in the second sonata. Thus these quartets, fine and free in style as they are, are not the fullest expression of Mozart’s genius, as the series of six dedicated to Haydn may be taken to be.
There are, as we have said, twenty-three quartets in all. The majority of the early ones were written under the influence of a certain mode or style, as experiments or as test pieces; and the last four were written with the purpose of pleasing the public or of suiting the special abilities of a king of Prussia. Only the six quartets dedicated to Haydn may be taken as what Mozart felt to be his best effort in the form, the expression, perfect as far as he could make it, of his highest ideals. As such they are almost unique in his music.
With the quartets may be mentioned the four great quintets for strings, written, two in the spring of 1787, one in December, 1790, and one in April, 1791. Of the combination of five string parts Haydn made little use. Boccherini, however, had written at least one hundred and twenty-five quintets. He was himself a 'cellist and, as might be expected, the added instrument in his quintets was a 'cello.
Mozart added another viola to the group. Though this added no new strand of color to the whole, it rather complicated the problems offered by the quartet. As Otto Jahn has carefully explained, with the volume of sound thus thickened, there came a need for even more active movement of the separate parts. Since the additional part was among the middle voices, the outer voices must be spread as far apart as possible so as to allow sufficient freedom of movement to the inner. The extra viola might be treated as a bass part to the first and second violins, or as the upper part above the other viola and the 'cello. Mozart made use of this possibility of contrast nowhere more clearly than in the opening pages of the quintet in G minor.
The four quintets are respectively in C major (K. 515), G minor (K. 516), D major (K. 593), and E-flat major (K. 614). Of these that in G minor is clearly the most remarkable; and it is indeed conspicuous above almost all his instrumental music, for the passionate intensity of the moods which it voices. Needless to say it still holds its place as one of the supreme master-works in chamber music. More than a similarity of key unites it to the symphony in G minor. The themes in both works seem much alike, and both are equally broad in form and full of harmonic color.
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