. 29, No. 39 (here the _da capo_ is considerably changed).

In No. 37 the "subordinate song" is represented by no more than a brief
Interlude (measures 33-40) between the principal song and its
recurrence,--just sufficient to provide an occasion for the latter
(which, by the way, is also abbreviated).

Mozart, pianoforte sonatas: No. 2, _Andante cantabile_; each song-form
has two Parts; the subordinate song changes into the minor.

No. 9, second movement, _Menuettos_; the subordinate song is marked
"Menuetto II," a custom probably antedating the use of the word "Trio"
(see Bach, 2d English Suite, _Bourree_ I and II).

No. 12, _Menuetto_.

Schubert, _Momens musicals_, op. 94, Nos. 1, 4, and 6.

Schumann, op. 82 (_Waldscenen_), Nos. 7 and 8.

Chopin, _Mazurkas_, Nos. 6, 12, 23, 47, 50. In Nos. 10, 45, 46 and 51,
the subordinate song consists of one Part only, but is sufficiently
distinct, complete, and separate to leave no doubt of the form.

Also Chopin, _Nocturne_ No. 13 (op. 48, No. 1).

Examples of this compound Song-form will also be found, almost without
exception, in Marches, Polonaises, and similar Dance-forms; and in many
pianoforte compositions of corresponding broader dimensions, which, _if
extended beyond the very common limits of the Three-Part form_, will
probably prove to be Song with Trio. This the student may verify by
independent analysis of pianoforte literature,--never forgetting that
uncertain examples may need (if small) to be classed among the
group-forms, or (if large) may be suspected of belonging to the higher
forms, not yet explained, and are therefore to be set aside for future
analysis. Mention must be made of the fact that in some rare cases--as
in Mendelssohn's well-known "Wedding March"--_two Trios_, and
consequently two _da capos_, will be found.

CHAPTER XIII. THE FIRST RONDO-FORM.

EVOLUTION.--It cannot have escaped the observant student of the
foregoing pages, that the successive enlargement of the structural
designs of musical composition is achieved by a process of natural
growth and progressive evolution. No single form intrudes itself in an
arbitrary or haphazard manner; each design emerges naturally and
inevitably out of the preceding, in response to the necessity of
expansion, and conformably with the same constant laws of unity and
variety,--the active agents, along the entire unbroken line of
continuous evolution, being _reproduction_ (Unity) and legitimat