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THE TWO-PART SONG-FORM.
THE SONG-FORM OR THE PART-FORM .-- Almost every musical composition of average (brief) dimensions, if designed with the serious purpose of imparting a clear formal impression, will admit of division into either two or three fairly distinct sections, or Parts, of approximately equal length.

The distinctness with which the points of separation are marked, and the degree of independence of each of these two or three larger sections, are determined almost entirely by the length of the whole.

And whether there be two or three such divisions depends to some extent also upon the length of the piece, though chiefly upon the specific structural idea to be embodied.
A composition that contains two such sections is called a Two-Part (or bipartite, or binary) form; and one that contains three, a Three-part (tripartite, or ternary) form.
Such rare exceptions to these structural arrangements as may be encountered in musical literature, are limited to sentences that, on one hand, are so brief as to require no radical division; and, on the other, to compositions of very elaborate dimensions, extending beyond this structural distinction; and, furthermore, to fantastic pieces in which the intentional absence of classified formal disposition is characteristic and essential.
The terms employed to denote this species ("Song-form" or "Part-form") do not signify that the music is necessarily to be a vocal composition of that variety known as the "Song"; or that it is to consist of several voices (for which the appellation "parts" is commonly used).
They indicate simply a certain _grade_,--not a specific variety,--of form; an intermediate grade between the smallest class (like brief hymn-tunes, for example), and the largest class (like complete sonata-movements).

An excellent {84} type of this grade of Form is found in the Songs Without Words of Mendelssohn, the Mazurkas of Chopin, and works of similar extent.
The word Part (written always with a capital in these lessons) denotes, then, one of these larger sections.