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ENLARGEMENT OF THE THREE-PART SONG-FORM.
REPETITION OF THE PARTS .-- The enlargement of the Three-Part Song-form is effected, in the majority of cases, by simply repeating the Parts.
The composer, in extending the dimensions of his original design, resorts as usual to the most legitimate and natural means at his disposal--that of _repetition_.

By so doing, he reinforces the principle of Unity, and, instead of obscuring, places the contents of his design in a stronger and more convincing light.

It is true that the act of mere repetition involves the risk of monotony; but against this the composer has an efficient safeguard,--that of _variation_.

He may modify and elaborate the repetition in any manner and to any extent that seems desirable or necessary, the only limitations being that the identity of the original Part must be preserved beyond all danger of misapprehension, and (as a rule) that the cadences shall not be altered.
The act of repetition is applied to the First Part alone, and to the _Second and Third Parts together_; very rarely to the Second Part alone, or to the Third Part alone.
EXACT REPETITIONS .-- When Part I,--or Parts II and III together,--are to be repeated without any changes, it is customary to employ the familiar repetition-marks (double-bar and dots); with "first and second ending," if, for any reason, some modification of the cadence-measure is required.