III. A SONATA BY PHILIP EMANUEL BACH.
Sonata-form, historically speaking, first takes definite shape in the work of Philip Emanuel Bach (1714-1788), the most distinguished of the sons of the great Sebastian Bach. Though not a man of the highest creative genius, C. P. E. Bach possessed an ingenuity and a pioneering spirit which led him to make innovations so important that Haydn and Mozart freely acknowledged their debt to him. Feeling that music in the polyphonic style had reached its full development, he was original and adventurous enough to seek new means of expression and a novel combination of features of style already familiar.
In order to understand the situation that confronted him we must put aside temporarily the impressions we have received from the Andante of Haydn and the Rondo of Mozart, since both these compositions were produced at a time when his influence had already made itself felt. He had to face the problem of writing instrumental music that should be free from the constraining influence of the dance, of polyphonic style, and of the elaborately ornamented style of operatic music. He had also to find out how to unify a long piece of instrumental music by co-ordinating all its parts. The only solution of these problems lay in inventing what might be called pure instrumental melody: i. e., melody that was essentially expressive in the particular medium employed—the piano, the violin, the orchestra—and that was unhampered either by strict poetic or dance forms, or by the peculiar phraseology of polyphony. He did not, to be sure, entirely achieve this; we find evidences of both the older styles in his music. But an examination of any instrumental masterpiece of Beethoven will reveal how much he owed to the pioneer labors of C. P. E. Bach.
We must here caution the reader against the supposition that music at this particular time leaped suddenly forward. The tendencies that we have been speaking of were latent long before Philip Emanuel Bach appeared, and there was no strict line of demarcation where one kind of music stopped and another began. Organic development never progresses in that way; each phase of it begins slowly, becomes eventually operative, and dies as slowly as it began. And there were other composers working at that time on the same problems; composers who were of considerable importance then, but whose names are now forgotten.