The processes by which this was accomplished in harpsichord music may be briefly touched upon. The first theme tended towards simplicity. Already in sonatas of Christian Bach and Jean Schobert a dignified and somewhat declamatory type of melody is favored for the opening. This was usually repeated, that it might be impressed upon the mind of the listener. Often it came to an end squarely in a full tonic cadence.
The transitional passage which was then to accomplish the modulation to the dominant or relative major key in which the second theme was to be announced, tended to become highly conventional, a sort of service music with little more than formal significance. Usually a figure of some technical brilliance carried the music along in repetitions that could not fail to attract the attention of the listener and arouse his curiosity as to what was coming next. These figures might or might not be fragments of the opening theme. The modulation to the desired key having been accomplished, the passage came to an end in a flourish or in a pause of a beat or two. No feature of the triplex form is more distinctive than these conventional transitional passages which seem to carry on the double function of porter and herald.
After the claim to attention had been thereby established the second theme was allowed to sing. The general tendency was to give to this second theme a gentler and more truly melodious character than the first. Here was the great domain of the Alberti bass, for instance. And following the second theme came another busy little passage, service music again, of which the duty was to bring the first section of the movement to an orderly close in the key of the dominant.
The treatment of the middle section varied. It remained always the part in which the composer exercised the most freedom. It might be long or short, in the manner of a fantasia; it might merely present fragments of the first or second themes or both in a series of modulations or sequences. It may be said that the tendency towards a more or less dramatic development made an appearance before the end of the century, as if the composer was submitting his will to the suggestions of the themes themselves. The greater the inherent vitality of these themes the more likely were they to assert themselves in this middle section and to reveal, as it were, the germinating power within them and color the section with their nature. The end of the section was more and more contrived to lead up to the last section in an obvious manner, either with a long run, a series of flourishes reaching a climax, or a pause, or anticipations of the coming theme.
The last section differed little from the first except that the second theme now appeared in the tonic key. The transitional passage was taken, along with the themes themselves, from the first section; but, relieved of one half its duty—that of bringing to pass a modulation from tonic to dominant—was likely to be considerably shortened. The closing measures, however, were usually an exact reduplication in the tonic key of those which had closed the first section in the dominant. The first section was always repeated, and so were the second and third, en bloc.
Such was the sonata form of movement which we have chosen to call the triplex form; a movement in three clear sections, made up of two themes appearing variously in each of them. The three sections are generally known in English as the exposition, the development, and the recapitulation or restatement; and what distinguishes them is the conventional figure or passage work which was used to mark them off, one from the other, and to stand as dividing line between the first and second themes. In the sonatas of Christian Bach all these things are clear and en règle; in Emanuel Bach they are obscure. They are clear in the works of the Mannheim group, and in those of the Viennese and Parisian composers who responded to their influence. They are clear in the sonatas and symphonies of Haydn and Mozart and can still be traced in most of those of Beethoven. Hence it would seem that in many ways Emanuel Bach, instead of being the source of the pianoforte sonata, stands very nearly outside the current of influences to which it really owes its most distinctive feature.
We may again define the sonata as a piece of music which is a conventional group of several pieces or movements, usually three, more rarely four. The movements are not internally related to each other. The bond which holds them together is only traditional. One of these movements, most often the first, is written in a form sprung of the love of Italians and Slavs for melody, known generally as the sonata form. The presence of a movement in this form in a group of pieces will give an unchallenged right to call that group a sonata.[24]
III
The pianoforte sonata was a sufficiently clearly defined product of musical craftsmanship, if not art, before Haydn and Mozart began seriously to express themselves in it. It is right then to summarize briefly the musical value of the chief sonatas before their day.
The many writers may be divided according to the countries in which they practised their art. In London are to be found P. D. Paradies (1710-1792) and Baldassare Galuppi (1706-1785), both Italians, and Johann Christian Bach, submitting almost unconditionally to Italian influence. In the London group too must be reckoned one of the most important men in the development of pianoforte music, Muzio Clementi. In Vienna the chief figure is G. C. Wagenseil; in Paris, Jean Schobert; in Berlin, Emanuel Bach, with whom may be reckoned Friedrich Wilhelm Rust, who, through his brother Johann Ludwig Anton, a pupil of Sebastian Bach, was clearly influenced by the works of the great masters.