4. MIXTURE OF CHARACTERISTIC TRAITS.—This process tends to affiliate the two distinct classes of larger or higher forms, whose respective characteristics were explained and compared at the beginning of Chapter XVI. Upon very careful revision of this explanation, and reference to the given diagrams, the student will perceive that the distinctive trait of the sonata-allegro form is the section of Development which it contains; and that of the three Rondo-forms is the absence of such a Development. Of the mixed forms under consideration there are two: one in which a section of Development is introduced into the Rondo (as substitute for one of its Subordinate themes); and the other a sonata-allegro, in which the Development is omitted, and a new theme (a sort of additional Subordinate theme) inserted in its place. In other words, a Rondo (second or third form—probably not the first rondo-form) with a Development; and a sonata-allegro with a new Middle theme, or Episode (as we have already called it).
The Rondo with Development is illustrated in Beethoven, pianoforte sonata, op. 27, No. 1, last movement; it is the third rondo-form, designed as follows:—
Principal Theme, Two-Part form (measures 1-24).
Transition (25-35).
First Subordinate Theme, period, extended,—or phrase-group (36-56). Codetta (57-72).
Re-transition (73-81).
Principal Theme (82-97).
Transition (98-106). Then, instead of the Second Subordinate theme, a
Development (106-138); followed by an elaborate
Re-transition (139-166), and a regular