the structure as a whole is tripartite. In this portion of
the movement the composer has an opportunity to improvise, as it were,
with his material, using one theme or both as already presented. Dry
and labored development sections may, of course, be found in certain
Sonatas and Symphonies, but in the great works of such masters as
Beethoven, Brahms, Tchaikowsky and d'Indy the development is the most
exciting part of the movement. The hearer is conducted through a
musical excursion; every device of rhythmic variety, of modulatory
change and polyphonic imitation being employed to enhance the beauty
of the themes and to reveal their latent possibilities.

Before going further, it is well to point out a confusion which often
arises between the terms Sonata and Sonata-Form. When we speak of
Sonata-_Form_ we mean invariably the structural treatment as to number
of themes, key-relationship, etc., of _any single_ movement within a
series.[92] By the term Sonata is meant a composition generally in
three or four movements, _e.g._, First Movement, Slow Movement, Minuet
or Scherzo and Finale; of which, in most examples of the classic
school, the First Movement--and often the last--were in Sonata-Form.
An alternative name, indeed, for Sonata-Form is First Movement Form.
Beginning with Beethoven, however, composers began to exhibit great
freedom in the application of the Sonata-Form. We find Sonatas of
Beethoven, notably the set op. 31, in which every movement (even the
Scherzo) is in Sonata Form or a modification thereof; on the other
hand, there are compositions, entitled Sonatas, in which not a single
movement is in pure Sonata-Form, _e.g._, Beethoven's Twelfth Sonata,
op. 26. These comments apply equally to many other large instrumental
works. For a symphony is merely a Sonata for Orchestra, a
String-Quartet a composition--of the same general type--for four solo
instruments[93] and there is, furthermore, a large group of ensemble
compositions: Sonatas for Violin (or any solo-instrument) and
Pianoforte; Trios, often for unusual combinations, _e.g._, Brahms's
_Trio for Violin, Horn and Pianoforte_; Quintets and even Septets--in
all of which the distinction must be made between the terms Sonata and
Sonata-Form. Nor is there any rigid rule in regard to number of
movements or the moods expressed therein. The classic Sonata, Symphony
or Quartet, as we have stated above, generally contained three or four
movements, of which the first