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 th same constant laws of unity and

variety,--the active agents, along the entire unbroken line of

continuous evolution, being reproduction (Unity) and legitimate

modification (Variety); or, in other words, modified repetition.

It is upon the indisputable evidence of such normal evolution in the

system of musical structure, that our conviction of the legitimacy and

permanence of this system rests.



The diagrams which appear on pages 78 and 98 partly illustrate the line

of evolution, which, in its fullest significance, may be traced as

follows: the tone, by the simplest process of reproduction, became a

figure; the figure, by multiplication or repetition, gave rise to the

motive; the latter, in the same manner, to the phrase. The

repetition of the phrase, upon the infusion of a certain quality and

degree of modification (chiefly affecting the cadences) became the

period; the latter, by the same process, became the double-period.

The limit of coherent phrase-succession (without a determined

interruption) being therewith reached, the larger Part-forms became

necessary. The Two-Part form emerged out of the double-period, the

two connected periods of which separated into two independent

Parts, by the determined interruption in the center. And, be it well

understood, each new design having once been thus established, its

enlargement within its own peculiar boundaries followed as a matter of

course; I mean, simply, that the two Parts did not need to remain the

periods that were their original type; the process of growth cannot

be stopped. The Three-Part form resulted from adding to the Two-Part

the perfecting reversion to the starting-point, and confirmation of the

principal statement. The Five-part form, and the Song with Trio

are enlargements of the Three-Part forms by repetition or

multiplication; and with the latter the limit of this particular

process appears to be achieved. Any further growth must take place

from within, rather than by addition from without.



But the process of evolution continues steadily, as the student will

witness. To one vital fact his attention is here called,--a fact which

he is enjoined to hold in readiness for constant application,--namely,

that perfection of structural design is attained in the Three-Part

form, and that every larger (or higher) form will have its type in this

design, and its basis upon it. The coming designs will prove to be

expansions of the Three-Part form.