disguises employed by the composer (for the sake of
Variety), he will find the whole piece reducible to a very few melodic
figures, announced at or near the beginning. See also No. 45 (C major),
No. 36, No. 26. Also Schumann, op. 68, No. 7, No. 8, No. 18, No. 23.
Also Beethoven, pianoforte sonata, op. 10, No. 2, last movement; op. 26,
last movement.

In musical composition this process is known as thematic development, and
it generally extends over the whole, or a greater part, of the piece.

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:--

[Illustration: Example 41. Fragment of Mendelssohn.]

Measures 1, 2, 3 and 8 constitute the original regular four-measure
phrase.

The following regular phrase (to be found in the last movement of
Beethoven's pianoforte sonata, op. 28):--

[Illustration: Example 42. Fragment of Beethoven.]

is immediately followed by this lengthy and elaborate extension:--

[Illustration: Example 43. Fragment of Beethoven.]

[Illustration: Example 43 continued.]

The portion marked _b_ i