Some of Sebastian Bach's most typical gigues have at least two distinct themes, while more than one of Haydn's ripest sonata movements derive everything from their first themes. Accordingly we may illustrate the true distinction of style by examples which refute superficial doctrines.
These two examples are almost exactly the same length, yet Haydn is beyond Bach's scope in the first eight bars. If Bach could have accepted so trite a theme as Haydn's, he would have postulated that it did not end with a bump: and bars 5-8 would have horrified him, for he would have supposed that a movement that began so vulgarly was condemned to continue in the same style. Bar 8, however, enters on matters that Bach had never known. In it the first bar of a new period overlaps with the last bar of the old; and therewith we are plunged into a polyphony quite lively enough for Bach, and quite unpredictable in rhythm and key, its fourth bar overlapping with the answer in A minor, and the viola and violoncello entering in F major at intervals of two bars. Then, arising from bar 18, there are four bars on the dominant of F, with that merely jingling figure (c). We need not set limits to Bach's intelligence, and we may suppose that such a composition would have convinced him that here was no trivial divertissement, as he called the non-polyphonic sonatas that were becoming fashionable in 1745, but a new art with enormous pos sibilities.
Bars 23-26 transform the two notes of (a) into rich sustained harmonies. Then figure (b) bursts out in a new type of phrase, built up in 3-bar periods, which the ear need not trouble to recognize as such in the general bustle. The third of these periods abandons the figure and makes a melodious close into 5 bars of cadence on figure (b) with upper notes that merge into (c), nicely phrased. It is idle to say that all this has more than one theme, and worse than idle to deny that Bach's gigue has at least two distinct themes, that of the beginning, and that in bars 29-36. But Bach's relatively uniform texture will tolerate neither inter ruption nor irregularity of rhythm.
Haydn's exposition groups itself clearly into bars 1-8, the first group (Hauptsatz), asserting the tonic and overlapping with bars 8-22, which effect the transition (plus the sustained chords 23-26) to the second group (Seitensatz) in F major, bars 2 7-40, with its cadence-phrase (Schlussgruppe) in bars 36-4o. These sec
tions could not be more distinct with any number of themes.
There are no rules whatever for the number or distribution of themes in sonata-form. When critics tell us that Mendelssohn is weak "in second subjects, where the human element is re quired," they disqualify themselves by a terminology as useless as that of the friend who did not see where the painter was going to put his brown tree. Any generalized criticism of sonata themes is bound to be nonsense ; for themes stand in endless variety of relation to the whole. They are details, which give pleasure in themselves as well as in their relation to the scheme. But it is foolish and vexatious to lay down rules as to what pleasure the details shall give. If you examine frescoes with a microscope or miniatures with a telescope you will not enjoy them; and if you expect Beethoven's "Harp" quartet to show you the purport of its first movement in its themes you might as well try to study foreign poetry through a traveller's phrase-book.
So much, then, for the vital element of drama in the sonata. Historically it originates wholly with Haydn and Mozart; and Philipp Emanuel Bach contributed to it nothing but a romantic rhetoric. His chief pride was in his invention of Sonaten mit verdnderten Reprisen; that is to say sonatas in which the repeats were written out in full in order to control the fashion of altering and amplifying the ornaments on repetition. Now, could any thing more clearly betray a non-dramatic style? The survival of repeats in the most dramatic works. of Beethoven and Brahms shows how powerfully an architectural symmetry can dominate a series of emotional tensions: but imagination boggles at the thought of using these repeats to display a new set of ornaments.
Haydn saw that the only place for C. P. E. Bach's device was in purely lyric slow movements. Even there he never had the patience to plod and pose (as C. P. E. Bach did to the bitter end) through a repetition of both parts. When his second part comes to recapitulate the second group it combines both versions. This form appears for the last time in history in one of Haydn's "London" symphonies, in the wonderful movement of which the theme is quoted in RHYTHM, Ex. i. Though "binary" it is manifestly lyric, and could no more be applied to active move ments than the Spenserian stanza could be applied to drama.