Its operation on a smaller scale, with more limited reference to one phrase alone, effects the development of the phrase by extension.
The process of extension or expansion, by means of which the phrase usually assumes a somewhat irregular length, consists mainly in the varied repetition of the figures or motives that it contains; and the continuity of the whole, as extension of the one phrase, is maintained by suppressing the cadence—suspending all cadential interruption—during the lengthening process. For example:
[Illustration: Example 39. Fragment of Mendelssohn.]
These six measures result from a repetition (variated) of the third and fourth measures of the original—regular—four-measure phrase. A cadence is due in the fourth measure, but it is not permitted to assert itself; and if it did, its cadential force would be neutralized by the entirely obvious return to (repetition of) the motive just heard. Further:—
[Illustration: Example 40. Fragment of Mendelssohn.]
There is no cadence in the fourth measure,—the current of the melody obliterates it and hurries on, voicing the last measure again and again until it dies away in the tenth measure, where a cadence ends it. That it should be the tenth measure is purely accidental; the number of measures is of little account in the act of extension; here, it was continued until a convenient place was found (with reference to chord and key) for the cadence. Further:—