This is no more nor less than might be expected from the dominion of the law of Unity.
The equally inflexible demands of Variety are satisfied by presenting this self-same leading thought in ever new and changing aspects,--_not_ by exchanging the thought itself for a new one at each successive angle.
This latter faulty process would naturally lead to a conglomeration of impressions, baffling comprehension and jeopardizing real enjoyment.
In a classic page of music we perceive that each successive unit grows, more or less directly, out of those which go before; not so directly, or with such narrow insistence as to produce the impression of sameness and monotony, but with such consistency of design as to impart a unified physiognomy to the whole.

Hence, it will often be found that every melodic figure, during a certain section (if not the whole) of a composition, may be traced to one or another of the figures which characterized the first phrase, or the first two or three phrases, of the piece.

This was emphasized by our reference, near the end of the first chapter, to the 8th Song Without Words of Mendelssohn.

If the student, in analyzing the melody of that composition, will endeavor to penetrate some of the clever 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.