rmine and justify the structural plan and
arrangement.

But the aims of the composer outnumber the regular forms, and therefore
modifications are unavoidable, in order to preserve the latitude which
perfect freedom of expression demands. The student may rest assured of
the existence of many irregular species of these fundamental forms (as
exceptions to the rule) and must expect to encounter no little
difficulty and uncertainty in defining the class to which his example
belongs,--until wider experience shall have made him expert.

All such irregular (or, in a sense, intermediate) varieties of form
must necessarily either admit of demonstration as modification of the
regular designs; or they will evade demonstration altogether, as
lacking those elements of logical coherence which constitute the vital
and only condition of "form and order" in musical composition.

To these latter comparatively "_formless_" designs belong:--all the
group-forms; the majority of fantasias, the potpourri, and, as a rule,
all so-called tone-poems, and descriptive (program) music generally.

On the other hand, those irregular designs which nevertheless admit of
analysis according to the fundamental principles of structural logic,
and are therefore directly referable to one or another of the regular
forms, may be classified in the following four-fold manner--as
Augmentation, Abbreviation, Dislocation, or Mixture, of the proximate
fundamental design.

1. AUGMENTATION OF THE REGULAR FORM.--To this species belong those
forms (small and large) which are provided with a separate
Introduction, or Interludes, or an _independent_ Coda (in addition to,
or instead of, the usual consistent coda).

For example, Beethoven, pianoforte sonata, op. 13, first movement; the
first ten measures (_Grave_) are a wholly independent Introduction, in
phrase-group form, with no other relation to the following than that of
key, and no connection with the fundamental design excepting that of an
extra, superfluous, member. The principal theme of the movement (which
is a sonata-allegro) begins with the _Allegro di molto_, in the 11th
measure. Similar superfluous sections, derived from this Introduction,
reappear as Interlude between the Reposition and Development, and near
the end, as independent sections of the coda.

In a manner closely analogous to that just seen, the fundamental design
of any movement in a _concerto_ is usually expanded by the addition of
pe