The simplest and most common means of enlarging a sentence is by the extension, or repetition, of the final cadence—that effect which is so frequent in the chamber and symphonic music of Haydn, and which has its comic manifestation in the so-called "crescendo" of the Rossini Operatic Overture.[60]
Haydn: Quartet, op. 74, No. 2
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As Haydn was an important pioneer in freeing instrumental structure from dependence on the metre of words, his periods are always clearly organized; the closing measures of this example seem, as it were, to display a flag, telling the listener that the first breathing-place is reached. Very often both the fore-phrase and the after-phrase have cadential prolongations, an example of which may be found in Haydn's Quartet, op. 71, No. 3. The two following illustrations (the first movement of Beethoven's Fifth Sonata and the third movement of the Fourth) furnish remarkable examples of extended 16 measure sentences; each sentence being normal and symmetrical at the outset and then, as the fancy of the composer catches fire, expanding in a most dramatic fashion. Sometimes the additional measures, in an extended sentence, are found at the start; a clear example of this is the first sentence (with its repeated opening measure) of the Largo of the Seventh Sonata. Sentences are also often expanded by the insertion of one or more measures in the middle of the phrase, e.g., the beginning of the first movement of the Seventh Sonata and the corresponding place in the Fourth. In the former sentence the first phrase is perfectly regular, but as we reach our final cadence only in the tenth measure, we must account for some additional measures. The polyphonic imitation of the descending motive of measure 5 makes clear that this measure has two repetitions. In the latter case we reach the end of the sentence in the 17th measure and careful counting, and consideration of the melodic outline, will convince us that the 9th measure, emphasized by the sf mark, is repeated.
When an extra measure is systematically introduced into each phrase of 4 measures we have what is known as "five-bar rhythm"—so prevalent in the works of Schubert and Brahms.
Schubert: Sonata in E♭ major
